Your girlfriend had normal periods after your sexual contact, so this rules out pregnancy
. The size of the breast getting bigger and her wt increasing has something to do with the diet, hormones or her psyche. Ask her to take diet in form of of Kilocalories 40-45 Cal/kg/day. Otherwise you can start on Orlistat
60 mg for 6 weeks, if you don't see any response you can increase the dose to 120 mg/day. This will surely help. Thanks.