It doesn't sound like your OB is very forthcoming with their information. When I was at my fertility clinic they told me every statistic and I would write it down. They were so thorough.
First I would keep track of my HCG and progesterone numbers, then CR lengths, HB's, sac sizes etc...
When I started going to the OB they were very laid back. The OB didn't even bother to check the beats per minute, he would just listen and say they were "normal". It would drive me crazy. I had to ask over and over what the numbers were, most of the time he would just say "oh the 150's" which to me meant he didn't measure the beats at all. My OB was so bad he wouldn't even show me the US screen or let me hear the heartbeats unless I asked him! I had heard the heartbeats so many time at the clinic but that didn't make it any less special. He was such an understanding gyno, it was a terrible shock to see how casual he handled my pregnancy as an OB.
It actually drove me so crazy that I ended up leaving my original OB (who I had been with for 19 years) and going to a different more high tech OB, who I totally adore and trust. I told them I am keeping scrapbooks for each baby and want to know what the stats are. I have since referenced my information several times on the message boards for when someone not as far along is looking to compare. I thought it might also be helpful to know if I ever get pregnant again. Now I just keep track of the heartbeats and their weight but I like to see how they progress every week. It is pretty interesting.