Tip of cat's is red. What can this mean?

I took him in to the vet almost 3 months ago. I thought he had a UTI. The vet didnt think so although he didnt even test his pee or anything! He squeezed his belly area and said it wasnt a blockage and didnt think it was a UTI because his bladder wasnt full. My cat pees pretty normally. He was peeing in the tub and outside the litter box quite a bit but since we added another box and fresh water all over the house, and actually scrub the litter box clean at least once a week, he goes a lot more often in the box. There is another male here, and the first male, Whiskers, sprays sometimes, but it is more due to the fixed female that wont let the males near her. After he chases her around for a while, he will then lick himself, and he will "hump" a furry blanket then lick himself when he is done. I noticed that the tip area of his is red compared to the rest of the . I looked it up and cant find a lot of info on it or the causes, except that it could be a UTI causing it and only one site I saw said that. I want to get him fixed, but I would like to take care of the problem of a possible UTI first, but the vet seems like an idiot who just wants my money without doing any real work to find out what is wrong. I mean he prescribed anti inflammatory pills last time, and I have no idea what for, he didnt even really say, so I didnt give them to the cat. Anyway is it likely that a UTI is causing it, or can it also be the fact that he is ually frustrated, and from that and the blanket, it irritated his ? I am going to take him to a different vet after the holidays, but I want to get some ideas first as to what it can be. I dont totally trust vets, as most I have delt with seem to mostly be in it for the money.