This is one of the worst thing you can possibly say to a person experiencing anxiety. I went to the doctor and everything was fine, anxiety creates ghost pains in chest, arm, stomach which make you believe you're experiencing pain just because you're focusing on it. I don't think a healthy 21 year old person with no heart disease family history has anything to worry about if he smokes some weed and start experiencing anxiety and chest discomfort/pain.
Firstly just to add you should consider going to see Chiropractor. There may be a problem relating to a trapped nerve in your back or foot or somewhere else. This could cause some of the spasms and pains you describe. If that is the case they could help you over a few courses of treatment.
I have seen one in the past due to spasms in my neck muscles which eventual made my back and all my neck muscles lock up, this led to migraines which crippled me for hours/days/weeks. My entire collage years were ruined by this and I never learned the solution until I was in my 30s. You have seen a doctor so it would be worth examining the possibility that is neuromuscular instead.
Especially since you say you lounge around a lot. Chairs are made for comfort but not for correct posture and can screw us up.
Secondly I gave up smoking weed for 3 years. Came back to it when I could enjoy it again. It was causing me anxiety so I stopped.
Its a wise choice to make in your situation. Bear in mind that every strain can affect you in a different way. Some still make me anxious, I just note them and don't smoke it again. Also it can vary in the same strain depending on when that strain got chopped, wether it had all amber and had gone a little longer or just cloudy trichomes. In all honest I think just stopping for a month or two will help, it cant hurt!
Lastly, to you and all the people who posted here I would just like to say its literally brought a little tear to my eye reading all your good advice and kind words on the matter. Its great to know there are people who show consideration, compassion and kindness towards each other still existing in the crazy world we live in.