I need help bad.

Nina ✊🏾🇺🇸
I'm almost 31 and I've never been pregnant. I've tried tracking my ovulation and I'm irregular. I've tried to get pregnant in my early years and nothing. I'm getting worried. The guy I'm with has 4 kids so I know it's not him. I don't understand what's wrong and I'm getting depressed about it. I need some advice on what to do or take.