17 / 18 months is prime time for separation anxiety.
My son got quite sick at 18 months with bronchiolitis and i spent 2 nights sitting on the rocking chair with him so he could sleep because if I tried to lie him down he just coughed non-stop. In the end I discovered (after 2 nights of not sleeping myself) that I could gradually lie down with him still on my chest and he would sleep like that (on my chest), but I could not actually put him down. He would fall asleep with his head on my shoulder, and if I tried to put him down he would wake up instantly, super upset (this was after 3 weeks of finally sleeping through the night). The only way I could get him down was to lie down on my back with him still on my chest, and then wait for him to naturally roll off me. That meant that he was in our bed for 2 weeks because there was simply no way I could get him into his cot.
In the end we bought him a "big boy bed" (normal single bed) and that way I could lie down like that and wait for him to roll off me and onto his own bed. After a week of having to get up countless times in the night to see to him, we finally just moved his bed into our room and squashed it between my side of the bed and the wall. He now sleeps there, and then at some point in the night crawls over and joins us in our bed.
In some ways i love the closeness, in other ways i long for my own space agian. But it has definitely resulted in more rest for all of us.
I was pretty convinced it was due to separation anxiety. I think he has passed that phase now although he is still in our room and still joins us in our bed sometime in the night (he's now 20.5 months). But I also think he feels more secure in this set up. We will move him back to his room at some stage but for now at least I can get some much needed rest whilst still giving him that security and comfort he needs.
Thankfully for me the day never got quite as bad as you describe, but he does frequently want "up" and there have definitely been times when he refuses point blank to go to dh, he just wants me, and he just wants me to carry him. It does get frustrating.
Frequently i use the loo with his sitting on my lap because as you mentioned, he doesn't want to go down.
He is in creche 4 days a week. He's with me at home on a wednesday (I don't work on wednesdays) and weekends, but at creche the other days. I find on the days that I spend a lot of time on my cell phone or laptop (even though i think i'm interacting with him at the same time), he acts up a lot more and "demands" my attention a lot more. The days when i make a point of not using my phone or laptop he is much much better and far more pleasant.
I think it's really hard for them spending so much time away from their parents at creche. Yes, they get on well with the teachers, but it's not mommy. Babies/toddlers have a special bond with their mothers (or some seem to have a closer bond with fathers), and so they really crave that time and closeness.
I do think the phase your daughter is going through will pass.
There are differing opinions on how to deal with it. Some will say to just set boundaries and refuse to pick her up all the time becuase you will "spoil" her etc.
I don't follow that belief at all. I honestly believe that if they are acting out like that they desperately need that closeness and reassurance etc. It won't last forever.
When you can, carry her around. If you can't, what I have found works an absolute charm in the kitchen is our 'steps'. It's a little 2 step plastic ladder thing (not really a ladder, but those 2 step things you buy so you can reach the top shelves of high cupboards). I could never put logan down in the kitchen and that's when i frequently need two hands. We've brought that out and as long as I put him on that so he can see what's happening on counter level, he's quite happy. If he can't see (example what's going on in the pots on the stove), then he asks for up again. But it at least gives me freedom to chop things and pack things and do other stuff in the kitchen.
I am lucky though in that he is usually quite happy to sit on my lap and read a story so that does give me a break from physically carrying him.
What is your morning routine like? And evening?
It sounds like you work really long hours so this might not be possible, but maybe if you could take just 10 min in the morning to play with her. Sit down on the ground and build blocks or whatever else she likes. Say to her at the beginning, "ok, lets sit and build blocks together, and then afterwards mommy needs to get ready for work. You can come and sit on the toilet while i brush my teeth" or something like that. Maybe that one-on-one focused time will help. And something similar in the evenings.
We feel that because we carry them around while we do xyz we are spending time with them, but it's not time focused ON them and i think that is what's important.
I really hope for your sake this phase passes soon because it really does sound like you're taking strain.
Oh, another thing, take 1-2 hours to yourself on a weekend or something. Just go do the shopping and leave her at home with dh. She will cry when you leave, but she will be fine. YOU need a break too every now and then. And it will be good for her and daddy to have some bonding time too.