The foreskin on my penis has recently tightened and will
Repeated trauma / infections....
I went through the details and understand the problem you are currently facing. Difficulty to retract foreskin does indicate a tightened foreskin. I assume you did not have this issue earlier. Repeated trauma due to rough intercourse, masturbation without proper lubrication or diabetes; as well as an infection can lead to foreskin tightening. It occurs due to odema and stricture formation.
We can treat this problem. But treatment is based on the cause. You need to consult a doctor for careful local examination. Until then avoid masturbation and sexual intercourse.
Hope this helps. Let me know if you need clarifications.