Starting Prometrium

Erin
It's my first month TTC. I have had extremely irregular cycles for years with bad endometriosis. I went 8 mos with no period, then regular for 1-2 mos, then I spotted for 2 weeks straight and immediately went into 5.5 weeks of a constant period of which 2.5 of those weeks were extremely heavy. So that ended, I was  testing with OPKs and ovulated this weekend. Tonight I start Prometrium 200mg. I take 2 before bed. What should I expect? I will have to take this every month until we get pregnant which we're obviously hoping won't take long. Looking for expectations and results stories on using this med.