Need some help!

Hello! I just got the app today in hopes that some of you can help me along. We have a 3 yr old little boy after 10 yrs of being told I'd never have kids. I was off birth control for 6 yrs and nothing. My pregnancy was not a fun one at all after 9 1/2 weeks hospital bed rest. But I've decided I'd like one more before 30. My cycles are psychotic. They will last 6-11 there's never a guarantee when they will show up either 😕 Everyone keeps telling me to start trying after ovulation ummm yeah because I totally know when that is with sporadic periods lol. I've thought about the fertility monitors but not sure I want to spend the $200 + and them not help. Any tips would be greatly appreciated.