I believe that there is a time after our surgeries that we feel great---we haven't done a great deal, but , for the most part, the surgical pain is gone and we think we are all healed up and ready to go.
I would, as the others have said, take a little bit longer to get up to speed, so to speak. You are doing a few things that your body is not quite ready for yet, and it is letting you know.
Remember what has been done to you surgically, and remember how long that it actually takes for your body to heal.
I do not know diddly about any equestrian stuff, but I do know that I was guilty of doing a few things too fast, as well.
Let your body rest, as you are doing things now that your body hasn't done for a while; it is also doing things now that you may have been compensating for while ago, too. Lots of rearranging of assignments down in the hips and the muscles. Some of this is new to them
We have a saying in officiating and in coaching---"mechanics is muscle memory." Perhaps, regardless of how many times you have done this in the past, your muscles have to relearn to do some of this again. Do you feel that your muscles are strong enough right now to handle the back-to-back sessions?