Need advice, exercise / coping with body changes?

Claire

So I'm 15 weeks and I had a bit of a breakdown the other day getting frustrated about not feeling like my "normal" self. I was in pretty good shape pre-pregnancy. First trimester was horrendous with vomiting and fatigue and I found it impossible to get any real exercise in. Now I'm starting to feel a little better and wanted to get back to more movement, but I just feel like I got so out of shape from the months I spent sick. I used to run and now just walking quickly will get me out of breath. Fast forward to this weeks emotional breakdown, I went on a hike with some friends and right toward the end it was getting really steep. Under normal circumstances I would have had no problem pushing on but I started to get super anxious about not knowing if I was pushing myself too far. I was afraid to stress my body out and cause some kind of harm to baby so I ended up stopping early and telling them I would wait for them until they were on the way back down. Then I sat to rest and call my husband and just broke down crying. It caught me off guard to get so emotional but I think I was just frustrated about feeling "weak" and upset that I didn't really know where the limit was for exercise and got so anxious. How do you know when it's time to stop exercise? I didn't feel awful and still think maybe i could have gone on, but I just felt like I would feel so guilty if something bad happened. How do you build back up to exercise after the first trimester misery? Sorry for the long rant! Just needed a place to vent. Picture of the pretty hike to not get lost!