What should I think

I asked my boyfriend was he in love with me or does he just love me. And he replied I love you and I could see us getting married but we have a long way before we get to that. Okay what I do understand is that we only been together for 6 months and we've been living together for 3-4 months. Yes it's fine to not be completely in love but he says things like let's go get married tomorrow blah blah. Like for myself I think I'm actually in love with him UNTIL he started saying things like he would let his baby and his baby momma stay with him over the weekends if she wanted to after I talked about moving out for some space. And he takes his phone with him everywhere he goes! I had also lurked through his phone and found he sent a message saying hey beautiful to a girl. So I confronted him and he said oh she's just a friend we both do that she has a boyfriend. I'm like what?! How is that okay? Idk what to think because yes it's early on but my feelings are sooo deep into it ! Maybe because this is like my first relationship. What should I think? Is he just using me for the things I provide? Sex, watching his adopted son whenever he needs it, cleaning and cooking everyday? I'm 20 btw