getting very frustrated

So i got my first recovery period just over a year ago, and since then have had about 10 periods since then. The problem is that the ones i’ve missed are because every time i re-introduce weightlifting, my period threatens to go away again!! (lengthens out to about 50-day cycles). I’m getting really frustrated at this point. I’ve put in the hard yards for this whole recovery process, I’m 5’4 and weigh 70kg (overweight bmi) up from my lowest of 43kg about 4 years ago. I stopped all exercise about 2 years ago and put on about 15kg in those 2 years. Every time I exercise I fuel properly, adding in more food before and after. And I’m still gaining weight so I can’t possibly be in a deficit! I’m just really confused at this point. I’ve finished school and am currently only working a part time job so I literally got no stress on me whatsoever. Is it time for me to go and get a brain scan or something?!?