I’m sorry you had to experience this and I know that comments like this from someone you love so much can hurt. Your SO is still in love with you but there probably has been some communication issues perhaps? My suspicion is that your SO has wanted to say something about your weight gain for a while but hasn’t known how to bring it up because he cares about your feelings. But keeping his comments to himself has made them build up to this, which is definitely probably more hurtful. We are all human and your boyfriend can’t be perfect all the time. I know his comment hurt you but he has a whole complex array of emotions as well even if you feel they are not fair towards you at times.