feeling super nervous and worried :(

I had a MC back in February of '12 after 3 years of trying. A few months later and we had a second pregnancy that resulted it our awesome baby boy who is now 3 and a half. I just got this positive test on October 22nd...... I was So happy and thankful it was emotional for sure. Had an OB appointment  on the 27th, measured at 6w 6d and saw the little flicker of the heartbeat. With my first MC I don't think I saw a heartbeat flicker and it was at the 8-10 week mark (I don't really remember a lot about that time, I've tried to forget about it). With my son pregnacy I gained 100lbs, it was bad, but it was a combination of my own fault and my body not cooperating haha. Anyway I've been working hard for 3 years trying to loose the weight to get back to a good weight to try to get pregnant again. And bam it actually happened! Total shock! Anyway, I have been so nervous that I have stopped working out completely. I asked my OB about it and she gave me the ok, but just not to over do it, and to just watch out because moms tend to feel guilty that it was something they did to loose the baby. So I just decide to take a break and really just focus on eating healthy still and resting. Today I was just super antsy, I didn't want to go to the gym, but I decided to take my son to the zoo to walk around and enjoy the day. It was a nice day and I at least felt like I was doing good by walking, after 2.5 hours I started having a little cramping but it was close to closing time so I just finished up around the zoo until 5. On the way home I forgot I needed to stop at target because duh, target haha. Ended up spending 2 hours walking around there! So a lot of walking. Now I'm home and I am feeling guilty and nervous. I feel like I'm on a verge of a fever, I'm having some cramps, and I'm super tired. I'm worried that my need to get out and walk really did put the baby in jeopardy :( I know I'm still not "out of the clear" but I'm just wanting things to be ok. My next appointment isn't until the 17th :(. I just had to vent :( trying to just relax now on the couch under a super comfy blanket :)