Is elevated heart rate a sign of early pregnancy?

I'm getting symptoms that I've only ever had when pregnant before (heartburn and hiccups) but now I'm starting to realize that my heart rate elevates after like no effort. I got undressed and jumped into bed, i could feel it beating in my chest. Run up the stairs? Cue heart beat. Yesterday I took the garbage out and there's a small hill to get back to the house and my heart was pounding. Why it's confusing me is that there's no change in my breathing at all, because I've barely made any physical effort. I'm constantly getting cramps and sharp pains in my uterus (not on my period). I cried when my roommate got something off the top shelf for me last night because it was "so nice of her". I'm on nuvaring, a little under 200lbs if that makes a difference. It just wouldn't make sense because I've barely been sexually active and I am on birth control, but I can't help but wonder with all these weird things my body is doing. Thoughts?