TL;DR: I'm afraid my girlfriend is cheating on me.

Hello guys. I've been lurking trp for quite a while now, but finally decided to call for help regarding one of my own problems.(Hopefully someone else in my position will learn from this as well). (Also, throwaway because GF knows Reddit username.)

If you feel like i'm missing some details, please let me know.

But anyway, let's get started.

I'm a guy, 19y/o, who has been in a couple relationships(4), and so far i have never felt so insecure as i do right now. And at the same time, never so in love. But the problem is, i have this awful gut feeling about my girl. I have read the posts on here regarding gut feelings, but i didn't seem to find an answer that matched any of my concerns.

The thing is, i think she is wonderful, and i love her and she loves me even more, but because of her slutty past i just can't seem to get these thoughts out of my head. She is 18y/o, and have been with 18 guys(The legal age for sex is 15y/o in my country, but her fuck count is still 2x of normal standards). And that's not really a big deal, but i'm just afraid that she won't let go of her slutty past.

We've been together for a couple months now, she's my fourth girlfriend and i'm her first boyfriend ever. She also says that i'm the best she's ever had sexually, and all her girl friends tell me that as well(We have a lot of mutual friends). But i just have this feeling in my gut that she's gonna hurt me at some point in our relationship, because of the type of person she was. With me, she is sweet, loving and caring etc. all that stuff.

I'm very honest with her, and i don't have any big secrets, but i just can't tell if she feels the same way about me. We're together almost every day of the week, and she usually sleeps at my place, unless she has to go to work. We live about 2 hours apart from each other, in our own apartments, so there's a little distance, but other than that, there's no reason for me to be afraid. I just still feel so insecure and paranoid, even jealous. And that makes me feel like i'm not being man enough.

I have had almost double the amount of sexual partners she has, and i may or may not have cheated in previous relationships, but with this one i would never even lay eyes on another girl, they're just not interresting anymore. She is also quite jealous herself, probably because of my past too, and she has directly asked me never to cheat on her.

But i still feel like there's something wrong, even though i have no evidence pointing towards it. She have told me a bit of white lies about stuff unrelated to sex and the like, and so have i, but i still feel like there are some other small things she won't tell me about, and my insecurity kills me.

I just don't want her to be with a guy who has these thoughts about her, if theres is nothing going on. But i also don't want to be in a relationship where there is a chance of getting my heart broken, been there done that.

What i need to know is, if there's reason for me to be concerned? How can i strike up a conversation about this matter, without sounding like a jealous beta male? And what should i tell her?

Also, sorry for being grammatically incorrect, English is not my first lang. :)