I'm 45 And About 60 Pounds Over Weight, Iv Smoked

I'm 45 and about 60 pounds over weight, Iv smoked pot for about 30 years, and had colon cancer three years ago. Ok that's a bit about me here is the problem. About a week ago I completely stoped smoking cold turkey and immediately started working out at the gym. The last two days Iv began to treadmill jog for about 29 min. When I go home and in the shower I noticed blood after I spit. It goes away right away. Any thoughts, I'm pretty sure it's coming from my lungs.