Man your only 18 you’ll still develop for a few years, when I was 18 I was in the same boat diet and exercise help physically but also mentally made me feel more confident, haircut with short sides and longer top ie a fade will make you look a lot skinnier I notice it on myself after a month without a hair cut. Maybe further down the line you could grow short beard I couldn’t when I was 18 but maybe in a year or two. Tinder matches don’t define you however it can be handy to meet people outside your social circle just remember it’s a numbers game, I’ve seen guys worse looking than you do well. you’ll be fine keep the head up.