Pregnant and worried

Hey lovely ladies, I just found out that I'm pregnant (literally only 4 weeks today), and my husband and I are ecstatic (we've been ttc for a few months). But now I'm terrified that something bad is going to happen. I'm refusing to cross the road without waiting for the lights, and everytime I go to the toilet I'm afraid I'm going to get my period. Since it's so early I'm well aware that I could have a chemical pregnancy. I'm also going ice skating today and I'm worried someone is going to crash into me, or can they not do any harm this early?? Also, I've been having 150mg of caffiene a day for the past few years, now I've cut down to 75mg, the daily guide for pregnant women is 200mg so I should be fine right? Anyhow, is it normal to be this terrified or am I just overly-paranoid?