I don't have a prolactinoma, but I do have a large pituitary tumor (*supposedly* non-secreting, though testing has shown that relevant hormone levels are askew). It hemorrhaged sometime late last year, though doctors have tried to assure me that this can be positive. Of course, they also tried to assure me that it couldn't have caused a sudden worsening of symptoms (and 15lb weight gain in a couple months) in that same time frame, so I'm not sure how much I buy that.
I'm not on medication for it, but am trying to treat the hormonal imbalances with customized hormone cream. It's slow and takes a few months to make a discernible difference, but it's worked for me in the past. I find that as the levels normalize, the weight does start to come off (albeit a little more slowly than for most). I'm not quite in your boat, but I definitely sympathize, having just come out of a few very rough months where what I did just didn't matter -- my body and the scale had other ideas.
I hope your course of treatment can help you get your body back on track! I have no doubt that as your levels normalize, you'll start seeing results. Just hang in there