So tired of trying

TTC for 2.5 years. Me and my SO have been together 4.5 years. I do have 2 kids by my previous relationship. They are 9 and 6. I had a miscarriage back in June. I'm getting so stressed out with trying. Every month I think I have possible pregnancy symptoms and every month I get bfn. This is my 3rd cycle in clomid. This month we bd every other day and progesterone levels were 27.6 which is great but I'm 2 days before expected AF an got bfn today. Really thought this cycle was it I've had cramps for the past 4 days on left side, boobs a little sore. So bummed out. Why do drug addicts or horrible parent who don't even want kids pop them out so easily? I'm gonna be 30 y/o this year and feel like my clock is ticking we want 2 more babies. Just needed to vent. Thanks for reading.