hello,
has your doctor given you anything for your anxiety, being pregnant, I dont know what would be a choice of med, but michellepetkus post has some good ideas for nerves and anxiety. I hope you feel better.
You might want to post your question in the pregnancy section so other mothers who had this happen can give you advice. I would say try to drink lots of water and see if that helps though being pregnant it might make you need to use the restroom a lot. What did the doctor say to help it? Just to reassure you 165 is not super fast. It is the rate most people get to when working out so your heart can handle it. Just try to do some deep breathing and relaxation to see if it helps. Avoid caffeine and sugary foods and just rest as much as you can. Best of luck with the baby.