First of all, congratulations, and if you choose to continue with the pregnancy you should keep in mind that this is YOUR baby and YOUR pregnancy, not M's.
You do not have to choose the things she chooses, and you should also tell your partners that they should s l o w d o w n... Yes there are considerations, and you will need to speak with your health care provider about whether staying on the meds or going off them is the better choice. You should not just have a knee jerk reaction to stopping the meds, and neither should they. A mommy who is off her much needed psych meds is not necessarily better. It is a risk assessment situation.
Are you still in therapy? You should probably have someone to talk to about the feelings that can come up around weight gain in pregnancy. It is not easy even for women who dont have pre-existing eating disorders. You will need to learn to trust that your body will gain only what you need to support the pregnancy. This is a process, but you can do it.
It is also common for women to feel very differently about sex in pregnancy. Some are more sexual and some are less. Both are normal. Just find your new current normal and ask your partners to help you adjust. And interview different types of providers, docs as well as midwives. One will likely resonate with you more than the other and help you feel safer about moving forward.
One day at a time...