Hair Loss

I know that there are a bunch of different reasons why a cat might be losing its hair, but I'm not even sure if this is something that needs to be looked at or if its something that I caused.

I use a Furminator on my cats and while they all put up with it, none of them let me use it for more than a few minutes at a time. Then there's Marmalade, who apparently LOVES the furminator.

I was brushing him last night and he was purring like crazy and kneading me while I was doing it. He is a DSH but his fur is really thick and he sheds a lot in general, so as I was brushing clumps and clumps of fur I didn't really stop to look at his coat. I just kept brushing, he kept purring and I ended up with a huge ball of fur that had been brushed off of him.

Then later that night I took a closer look at him and realized that there were patches of fur that I had brushed almost completely out. He doesn't have any specific bald spot - just a few patches where his fur is incredibly thin and you can see his skin.

He has no other health problems that I know of and sees a vet twice a year for regular checkups.

So I guess my question is - is this a problem? Or did I just brush him way too much, causing him to lose the hair?

I feel really stupid if it was my fault because based on all of my other cats, they run away from me when they've had enough of me brushing them. I would have thought he would do the same (he tends to bite if he gets annoyed about something) and he didn't. So the fur was coming out VERY easily and I think I could have brushed more out if I had kept going.

Does anyone have any insight on this? Am I just a stupid owner who didn't know when to stop brushing my cat? Or do you think he has some hair loss issue that needs to be seen by a vet? I'm honestly perplexed about this because in an obvious way it seems like I just brushed too much and pulled too much out, but why wouldn't that have hurt him or bothered him if the fur wasn't coming out to begin with?

His skin looks completely normal and I've never noticed any bald spots or thinning spots before. The only thing I've ever noticed is that out of all of my cats, he sheds the most.

I usually only use the furminator once or twice a week anyway. And usually its when I'm sitting on the couch watching TV and a cat happens to stroll by. They get scooped up and furminated for a few minutes. I've used it on Marmalade before but this is the longest he's ever sat there for me, and I know I lost track of time. It was easy to do when it wasn't acting annoyed. Between the purring and the brushing I think I was kind of lured into a brushing trance . I just can't believe he let me go on for that long! This is the cat that bites when he's annoyed and thats a habit we've been trying to break. He bites when he's done with you petting him. He bites if I'm handing out treats and he's not getting one at that exact moment. Basically he just bites when he's annoyed and/or wants something. So I assumed that he would have bit me if he was done with being brushed. I guess its good to know now that he really likes being brushed. I'm just going to have to be a little more aware the next time it happens!