Are you saying that you can have an orgasm, but just have problems having semen come out (ejaculating) on occasion?
Have you had your testosterone level checked?
No, being overweight would not lead to a urethral stricture. However, if the foreskin is too tight, this can lead to problems with blockage of urine flow. It is never too late to do a circumcision of the foreskin is the problem. You will need to see a urologist to see if you may benefit from a circumcision.