Dont know what happend

1 had my period od 16.11 regular. 12.12 i took blood test here is cheaper to do that, beta was 1.3 14.12 my period should start but i had only spoting, yesterday i had normaly bleeding for first day of cycle but now my period stopped, i have only spotting. This is 4 year of my trying to get pregnant, I always have heavy cycles and they're always 7-8 days. I dont know what happening right now. I visited my doctor last month and he say that everything is perfectly fine with me but why im not getting pregnant. My cycle is on 29 days i track my ovulation and really think to give up 33