Is a low sex drive at 19 normal?

My boyfriend and I have been together for a little over 3 years.. At the beginning I had a lot of sex drive when I was younger but now I feel that as I got older, it’s so much lower, I don’t crave sex at all or don’t think about it and don’t get horny... Any tips? Is this normal? Can I do something to improve it?

My boyfriend never forces me to do anything but I feel like I’m letting him down every time I say no.. I always cba to start or don’t get turned on but sometimes when I do start I enjoy it a lot and our sex is amazing... so like? what’s wrong with me..? it’s so hard to start and get horny in first place!