Honestly hun, I can't make a true judgement on what I would do, because I am not in your situation. If you follow your head, will your heart start to agree, or will it cause issues between you and DF? If your weight wasn't an issue I understand from your post that you wouldn't even consider the drugs at this stage, so is your weight as much of a sticking point as your desire for a baby? If you could ensure that you were completely healthy, with regular gentle exercise and healthy diet through your pregnancy, would that mean that you weren't as worried about your weight?

Good luck making a decision hun, I know it is an incredibly hard one, so think it through completely and thoroughly, and I know you will come to the right decision for you and DF.