Confused as to what a dog means?

So I found this springer spaniel, it was on the middle of a road with no owner around so I threw it's stick to get it off the road and it followed me home. While drying it I crouched down and it sat closer but it's tail was not wagging. It then lay down on me, on it's back. I don't know what this means? I dried it like this. Left it and it started crying so I sat down across from it and it came over and it lay down on me. It didnt wag it's tail though. I don't know if it's friendly though because when it lies down it just looks at me so I don't know if i bend down to clap it if it will bite me or...? Any help?