Condoms? Won’t affect your weight and are pretty reliable. I can’t use hormones at all because they cause me to have seizures (I have epilepsy) so that’s what I’ve always used. You could also use a cervical diaphragm or sponge if you don’t want to do the condom, I know it can be hard to use a condom every time with a long-term exclusive partner, and those are also pretty reliable barrier methods that won’t affect your weight but feel a lot more “freeing” than a condom lol. When I was researching options my doc told me that the Nuvaring and the patch have by far the lowest side effects for hormonal birth control, and the copper IUD doesn’t have hormones so it’s supposed to have few side effects as well. Good luck!