Postpartum Question

So my baby is 3 months old. The first two months and had s period every other week but now I haven't had one in a month. Me and my husband are sexually active but I have no birth control. The pills don't work for me and I can't get that little insert thing becaus I am prone to ovarian cist. I am currently researching other birth controls but don't feel comfortable enough about any of them.... I just want to know if my period being all messed up is normal.. Thank you in advance