Guy suddenly has no time for me

Just looking for some advice :c

So, I met a guy about over a month ago and we've been talking since. We both like(d) each other a lot, and we both have established that we want(ed) a relationship together, and a lot more. Everything was great - almost too great - initially and now (since the start of May) he hasn't been treating me the same. Before, he would spend time with me almost everyday, text me everyday (he still does, but he barely did the day I'm writing this). All conversation was really friendly and lovey dovey kinda stuff. Some sexual. Now, he spends no time with me, he still texts everyday but it doesn't feel the same and it feels like I have to force a conversation out of him and I always message first.

He suddenly stopped spending as much time with me since his friend came back [from a trip]. He's been hanging out with her and some other friends pretty much daily since early May. He says this is because he didn't see her at all for 2 weeks. Fair enough, but the transition from him spending time with me everyday, being super affectionate, etc. to being nothing like that ever since she came back doesn't sit right with me. He's mentioned this girl before to me, and always refers to her as his mate. He's made it quite clear that they're just friends and he's even said that she'd never be interested in him.

He says that him not spending time with me is a recent thing and it won't be like that all the time and that he's hung out with his friends this much (like practically everyday) since way before he met me and that it's normal for him so I shouldn't worry [about him not liking me anymore, etc]. He's assured me that he still likes me, and he still wants me but the way he's treating me doesn't feel right and it's really confusing and hurtful. He also says he misses me all the time and he wants to spend time with me but he cant. But he doesn't really show that he means it, he just says it. I know I should just trust him but something just doesn't feel right.

I don't know if this is normal, and I feel that I could be overthinking and expecting too much considering I'm not his girlfriend officially. Also it's only been a month and a bit so... I've just not been in many relationships so I don't really know what to expect. I'm just scared because I really like him and I'm afraid that he doesn't like me anymore. My friends think it's too coincidental that he's stopped making me a priority since she's came back but I dunno. I just don't like how drastically he changed the way he treats me, it's just confusing. :c