I don't love my boyfriend, but he loves me

Okay, so to preface, I (19F) had an on-again-off-again relationship with my highschool sweetheart. He broke my heart two years back, but the heartbreak was too much and we dated again to relive that spark. That ended pretty quickly. So the break up was messy, but after two years, I've moved on.

I've been dating my new boyfriend (20M) for four months, and he's very inexperienced. Since I know what the first love is like, I expected him to fall in love fast, I just didn't think I wouldn't feel the same.

I do really like him and enjoy his company, but I don't feel that same spark, or the butterflies. He's not floating around in my mind 24/7 and I don't dream of marrying him.

Is this normal for a second relationship? Is it too soon to be dating again? I'm just lost right now. I also have no idea how long to keep going in this relationship, or when to decide it's over. Any advice?