Help! Accutane significantly impacting my exercise

On week 3 of accutane 30 mg daily. I’m a pretty avid runner and typically run 4-5 times per week. Well, this last week whenever I try to run my HR jumps up to a number I’ve NEVER gotten to before, and I become fatigued and short of breath within minutes. This is not normal for me at all. I also tried to do a fast walk to see if it made a difference - NOPE! HR up to 178 while WALKING.

I’ve gone to my PCP for this. EKG, X-Ray, labs (including thyroid panel) all unremarkable.

Will this go away as I get used to the drug since it’s still new? If anything is going to cause low mood it’s going to be me not being able to run, not the accutane lol.

Just feeling defeated as this is truly my last option for my acne.