New 'love' and worries

Hey guys,

I'd like to hear some other opinions about this, cause I don't really know what to do.

About 4 months ago I met a guy I got on well with and he fell in love with me, to me he was only a friend though.
After a few weeks I got to know his friend, who I clicked with right away. We started flirting and pretty quickly he admitted on having a crush on me and wanting to be with me, but that he wants to go slow. He told me a girl he met before loved him after a few days already and he couldn't understand that. Doesn't make sense...

Thats where the first problem starts, the guy I met first keeps talking bad about me, that I shouldn't be trusted
and that I will break his heart for sure. That gives me tons of pressure already, like I think I need to be careful with what I say around the boy I'm dating etc.

The second problem is, despite having suggested we go slow, he's already saying how much he loves me and that I'm perfect.
Now I recently dropped a lot of weight and am since enjoying flirting with men and that they look at me.
I admit I love the attention at the moment, cause I NEVER got any before.
On the other hand I already drown in it and it gets on my nerves quickly.

I mean I really like him and am attracted to him, but it's not love yet. Now a few days ago he said it again and I said it back without thinking. I felt really bad afterwards.
By the way, I haven't slept with him yet because I'm sticking to the 'going slow' part and my flirting...

Any ideas what I should I do? Thanks in advance ...