What’s the problem!???

Okay guys so I miscarried in June of 2019 and I haven’t had any luck since 😭 I’m not even sure I want to continue right now. We are a fairly young married couple (I’m 21 and he’s 23) but we’ve been trying for almost three years. Since high school I have gained a lot of weight and I don’t exercise as much as I should but, so I’m here to ask if that’s the first thing I should work one?? Should I change my diet and start a workout routine? I mean I do literally everything else. I take the stupid ovulation tests, I check my temperature, I’m checking my CM... what am I missing!! Please help! Give me the 411 😂