My mom makes fun of my for having stretch marks

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I’m 16 and pregnant and my body has gone through a lot of changes obviously. I’m 24 weeks and have gained 40 pounds all ready ( I was underweight prepregnancy) and as a result I obviously have stretch marks, my mom is constantly calling them ugly and saying my body will never be the same again (no shit) and my babies father/fiancé isn’t gonna wanna be with me when I’m done being pregnant and have gained at least 40 pounds. It makes me so self conscious even though I know it’s not true and I just wish she’d shut up about it. In this picture my stretch makes look a lot better than they actually are. Anyone got any advice on what to say to her to get her to shut up?