scared to try

I'm 20 and have been off contraception for 5 months. I was on the pill for 5 years. My period cycle is 35-38 days long. Not sure if it's regular yet. My partner and I decided to start TTC at the start of this month. After reading stuff on this app I've started to freak out. I don't track my cm or my bbt. Just when I have sex and when I get my period. Part of me doesn't want to try and just let it happen but then I don't want to waste any time. Is it okay to start off just having sex in my guessed ovulation window on my app and see if that works? I don't know much about ovulating or any of my symptoms I get. Please help me out I'm clueless