Hello Doc, For 2-3 Days Now My Penis Has Been

hello doc, for 2-3 days now my penis has been swollen. it swell and goes down on its own. i don't feel any pain or have any injury. i observed it after visiting the gym the previous day and i also feel tightness in my stomach like i am having constipation. i have tried eating lots of fruit and drinking plenty water. i am very worried i don't know what is wrong though my friend said i should relax it is the exercise i did, please what do i do?