Toxic relationship ?😔

Ever since I've been in my current relationship of 8 months we've been in love for 3 years we've only just decided to make it official but since it's been official I've lost a hell of a lot of weight and I'm talking about 3 Jean sizes, I've always been a size 10 but now a size 6 is baggy for me and my bones are showing, my mum is really concerned and thinks it's an eating disorder. I have anxiety too so that scares me about eating around him and lately I've been feeling depressed cause he's been really distant and I feel quite alone because it sorta feels he don't care. A lot of people are saying its a really bad thing that I've lost weight in a relationship but I can't seem to put it down to that , any advice?