Confused!

So I bought an OPK which I said I wouldn't because I have done enough cycle monitoring to know when I ovulating....or so I thought. However, I am confused because of my early period last month (cd 24 instead of 27). I don't know if I should assume that my cycle will go back to a 27 day cycle or if I should start peeing on the sticks now (it's day 8) just in case I get my period earlier again this month????
I have so much pain in my ovaries since my surgery and I really didn't expect it. Wasn't it the cysts that were causing the pain? It makes me paranoid that I already have new cysts because they really feel like the same pain as before my surgery just more painful. Also I have a constant shooting pain in my vajayjay which doesn't seem right.
I know I have no right to expect anything different but I am depressed that I didn't get preggo the last 2 periods since my surgery because I read that the first 3 months are the most fertile.