How to bring up the "are you still active on Tinder" question to the guy I'm seeing?

I've been seeing this guy I met on Tinder. We hit it off immediately and when we met for a first date the chemestry was obvious from both sides. We have had only 3 dates so far but it has been going great and it seems we can't get enough of each other while we're together.

However, I had my doubts on how serious he is and wether this is not only a fling to him (I asked him on our 3rd date whether he is in this only for sex and he said he isn't (also, I asked this question when we were making out and he was wanting to get intimate. His assurance was a reason I gave in (we didn't have sex but we did stuff in bed)).

So I opened my Tinder profile and saw that he has changed some of his pictures on his, thus, probably meaning that he is still looking around. It made me upset cause I feel like he should have said it to me while I asked the question on how serious he is.

So how can I bring this up in a playful and not-serious maneer? I don't want any big talks or dramas, but I feel like I was deceived and would like to understand what he is looking for exactly. Also, I admit I would like to still make things happen with this guy. Am I a fool for that?

Updates
+1 y
Would like to update my question by adding that the only reason I logged into my Tinder profile was to see any sings on whether he is still active on his. Sadly, I got the proof I was looking for : D... : (

I really like this guy and I thought he feels the same, so I'm not looking for anyone else at the moment. Perhaps, it was foolish.
How to bring up the "are you still active on Tinder" question to the guy I'm seeing?
Post Opinion