There are many people who do not appear to experience ‘runners high’. I am one of those people, I have never experienced any noticeable pleasant side-effects from exercise itself, just a rather unpleasant burning sensation in my lungs.
Have you tried exercising less intensely? I never got runner’s high until I started jogging in the low aerobic range, which is when you can speak in full sentences while running without getting out of breath (around 133 bpm for a 30 year old). If you’re getting a burning sensation in your lungs, you’re touching the anaerobic range (around 152 bmp for a 30 year old), which is too fast for a runner’s high AFAIK.
For me, coming out of competitive ameteur/high school sports, it felt unnaturally slow to learn jogging, even embarrassing at times, shuffling around at 8 km/h. Yet at the end there was regularly a runner’s high, and over time and mixing it up with higher-end aerobic exercises and anaerobic sprints, my aerobic running speed increased. I learned to be in conversation with my body rather than relying on external metrics, now I just run at a speed that feels natural and playful, varying from run to run based on how I feel in the moment.
I prefer the “can you talk in full sentences” measure as a low tech thing that more directly measures what you want. The right bpm varies with age and cardiovascular health and other factors, but the goal is to keep your blood well-oxygenated and whether you have enough breath to spare on talking is a more direct measure of that.