I am 6 weeks pregnant and want to get in better shape. Any tips for safe exercise?

I am very excited yet nervous to be pregnant again after a miscarriage over the summer. I took refuge in ice cream and alcohol after the miscarriage and tried to make the best of things by living it up and doing all the things I couldn't do when pregnant. Now I have been eating healthier and have not been drinking in the second half of my cycles for the last 3 months we have been ttc again, but I gained some weight and now that I am 6 weeks along I want to do whatever I can to safely get into better shape so I can strengthen my abdominal muscles to help with birth. I am also worried about back pain once I start to get big because I have some back and neck issues already, so I want to strenghten those muscles so I can handle the extra weight. I hate running but love hiking and being outside. I was thinking of joining the public gym which has a pool because I also like to swim though the idea of getting in a bathing suit scares me a bit. But what exercises should I be doing? Would it be better to join a gym or try and work out at home? Any tips on recipes for healthy nutricious meals? Are there any websites with aerobic or yoga exercises for pregnant women? Please help!