Chanz I cant help but smile, I have had your 'feeling' before many times.
Most times in my personal opinion its hormones that are changing how your body feels, ie bloatedness, moodiness, fullness of breasts etc.
I see by your ticker that you are CD16 now which means either just ovulated or about to. The ovulation could well be the reason you are feeling different and I would take that as a good sign!!!
Give another good go at BD and settle into the 2 week wait

Regarding the possibility of a cyst, with ovulation a cyst is formed called Corpus Luteum and is what makes the progesterone that we have with the 2nd half of the cycle and supports pregnancy for the first 12 weeks before the placenta is formed.
It can be quite big. With my pregnancy it was seen on the scan and was estimated at the size of a tennis ball. So I could feel it, and it caused some discomfort.
Once your body doesnt need the progesterone the cyst disintergrates again.