Boyfriend jerks off to girls on tiktok?

My boyfriend and I have been dating almost 2 years. He knows I have no problem Him watching porn and all of that. It’s a normal thing and I know he’s going to do it, so there’s no reason for me to get mad. But something that bothers me is that I’m almost 99.9% sure he jerks off to girls on tiktok. He follows accounts where girl show off their ass and boobs. Not naked but in certain clothes or shaking their boobs and ass. And I walked in on him watching something on tiktok and he cleared it real fast so I couldn’t see, but says that it was nothing... I’m honestly wondering if I’m overreacting. Again, watching porn just doesn’t bother me. I guess bc you go there for a nut, they are naked. That’s their job. But when you can jerk off to a girl with clothes on, on an app. It just makes me insecure and uncomfortable. Please someone give me some advice and your honest opinion. Am I overreacting?