There are certain days and certain runs when the endorphins flow.
It took me about 4 years of running before I started getting them. One day I went for a run in the local Royal Park on a horrid wet Autumn day, and I just got a rush.
Running before then wasn't a struggle as I start running to keep fit for other sports. I was use to going for the gym and doing exercise classes before then so I was toned and had some level of fittness but doing team sports meant I had to build my endurance up.
Now I suffer from a health issue that makes running unpleasant and lots of others sports off-limits, but when I can run I can still get the endorphin rush.
I suggest you go and get it properly diagnosised by a sports physio asap.If you in a running club get one recommended by someone there, else state your location and ask on this forum.
BTW my plantar fasciitis pain started in the arches of my feet not in the heel like other people and I didn't have problems on waking unless I had pain the day before. I also suffered from ankle, knee and hip pain until I sorted it out. However I do have old ankle injuries.