I think I have a masturbating addiction/problem

I'm 19 and have been with my girlfriend for nearly 2 years now.

For the past few months I've been so worried about the physical things we do together and me going too far during sex, when really it's not what I think and I haven't gone too far. I always been asking if I did anything bad after, so much that she's gotten tired of giving me assurance/clearance too and talking about these things as a whole.

Now that I've spoken to people and got over most of these things, I've calmed down and stopped thinking about them, but yesterday I realised an actual issue, which is that I get too *** when I'm by myself and touch myself way too often, sometimes even when I'm talking to her.

Warning about inappropriate content/masturbation before I get into this:

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We were on a video call last night, and I felt *** because she looked good and was wearing shorts. Then I kind of started touching myself, for a few seconds until I stopped, I think because I either felt she wouldn't like it, or wanted to focus on her talking to me, or both.

But again, at one point after, I went to the toilet and as I sat down I kind of wanted to do it a second time. I was telling myself not to but I kind of still did it - it was like a single "stroke" which felt good and then I moved my hand away, but I don't think it makes it better since I still gave in.

I didn't finish or get to the end, both times when I did it only lasted about 2-3 seconds after which I stopped and focused on my phone.

Shortly after, I started thinking about my actions and whether it might be sexual harrassment or something like that, because I didn't really tell her and was just doing it casually out of nowhere. I went to search if anyone else had similar problems and there were people saying it was creepy and really not normal. There were also people saying it was normal and the boyfriends were just being *** or affectionate, but I don't think so and I lean towards it being more creepy.

Aprt from being worried of going to jail for this, I feel really stupid and creepy now. Sure I didn't really think about it or know, but I did make the decision to do it in secret since she wouldn't like it and I see that it's not okay. I don't know what to do. 

I think it's also a bigger issue because I tend to do it often when I'm in my room, say if I'm watching a video or doing something and I get ***. I'm usually just in underwear unless I have to go out, so it's so easy to just start out of nowhere.

There's also been previous times in the past where we've been on the phone and I suddenly got turned on and started touching myself, albeit not to her like last night, but something like I see a video on the screen, or think of something that turns me on and I kind of touch myself. I did always end up stopping and focusing on the call/talking to her after a few seconds or so, but I still think it's bad. 

After learning how creepy it actually is last night, I know for a fact I won't be doing it when I'm on the phone with her unless she wants to, and I still feel really bad, but now I don't know if I should tell her. I feel like every time she's happy with me or talks to me she's only still here because she doesn't know I've stimulated myself in secret.

Can anyone give me advice on how to deal with this? Thank you in advance.