S.B.
You are probably right :) I would maybe have him checked just to be sure, but it is unusual for little boys to have UTIs and it is VERY common for kids to go through this stage.
I swear all six of my kids drove me to insanity with this phase. For some reason, there deal was even if we had JUST went potty at home, as soon as we got somewhere, the first thing they HAD to do was use the bathroom. It was like new bathrooms has some magical hold over them. If he is fully potty trained, you can say no, you just went potty 5 minutes ago, your big boy bladder can hold it until morning. I think the one thing you do want to watch is the control issue - it can get out of control pretty quick at this age.
If the dr. clears him I would go back to the timer system you probably used when you were training him. After a week or two, he will forget about using it as a control thing and move on to something else . . . like food, dressing himself, etc. etc. :)
Good luck!