I was almost obese, but worked hard to lose 35 lbs and got to a healthy weight. I'm only 19 but have stretch mark scars from the weight. There aren't many, and they will fade as I get more toned and treat them, but they will always be there faintly. I want to be able to wear a bikini but worry about the scars. I wonder if guys would find it gross.
First congrats on the weight loss, and second I'd say generally "no".
Often sex appeal is going to come first and foremost from more easily-noticeable broad features such as your proportions.
People tend to get very insecure about minor blemishes, scars, stretch marks, cellulite. I think it's because our society worships a kind of synthetic aesthetic in fashion and photography. My hypothesis for that is that this aesthetic became so prominent following what we found in illustrations of the male and female figure (line art, e. g.). Those often omitted those kinds of details in favor of simplicity and economy, and I think photography followed that.
I really think you have little to worry about if they're not excessive. Consider that there are morbidly obese women out there in bikinis sometimes, and a slender woman with stretch marks is probably going to look like a goddess in comparison.
Yeah with all do respect I'd prefer to see a girl without stretch marks (I'm into petite/skinnier girls). Honestly though at your age it depends cause like you said they can fade away so I'd really have to see you in person to tell if I found them unattractive or not.
Don't be too insecure about them, you have tried hard to get healthier and you have so congrats and honestly just dont care as much about how other people think about you in public. They want to think negative about you then let those fuckers think what they want. You control how you feel not them. Enjoy life and don't overthink everything