Getting discouraged

I have been ttc for 15 months with 1 chemical and 1 miscarriage. I am so tired of negative tests. Used preseed 2 cycles and still nothing. I am getting so frustrated. Everyone around me is pregnant or just found out they were pregnant. 😢😢😢 why can't I get pregnant. Doctor diagnosed me with pcos last year and with diet and weight loss I cleared that up. Doctors say bbt chart and keep trying. What else can I do ?? Please help any suggestions would be amazing.