cycle day 37-no period

I have an almost 7m old baby we were able to have through IVF. She's keeping me very busy, so I've just realized I haven't started my period. I'm currently about 36 days into my cycle. Once my periods came back after giving birth they were clockwork as usual. About 27-28 day cycles.... think it's a fluke I haven't started yet? We would LOVE to have another baby, even better if its natural. I just don't know how likely this could actually be... any others have similar experiences? What were the outcomes?