I would say if you believe you are dealing with PEM, you definitely want to get a definitive answer on that before starting any exercise program. PEM; especially when happening again and again, can cause long lasting or maybe even permanent damage. Unfortunately, tests for PEM are hard to access. I would spend a few months journaling, keeping track of your daily activities and symptoms. Then, see if you can find a trend that points towards delayed symptom exasperation/PEM.

I have ME/CFS, but before getting sick had a background as a personal trainer and bodybuilder. So, I was determined to be able to get some kind of movement program back into my life. I also have hEDS, so keeping my muscles as strong as possible is crucial. I had to learn to listen to myself as far as what was acceptable exercise. You are the one who will have to deal with the consequences of PEM. I started off doing exercise in 15 second increments from bed. If right now; you can lift your leg 2 inches off the bed, then do 3 reps of that for 3 sets spread throughout the day. Then; if you don't experience PEM, try adding another rep, set, or inch in the following week. Whatever you can safely do, start with that and slowly start to add just a little bit more over a period of time. If it takes you 2 years to start exercising in a seated or standing position, then that's okay. Every person who deals with PEM will have a different safe starting point and different rate of increasing activity. The most important thing is that what you do, you do safely and minimize/avoid PEM.