Gaining weight/bloated coming off contraception?

I wasn’t expecting this one, I came off the pill 6-7 weeks ago, still no period, all negative tests, so defo not preg, but dear lord I have gained weight! Probably a stone. I stopped counting the gaining lbs after 10 lbs. it’s just getting horrible. My stomache looks 6 months pregnant and I feel all the fat around my body it’s seriously stressing me out, exercises and diet hasn’t changed. But I think I’m retaining water from no period. What on Earth can I do!?!?