Hi Maya.
I'm Mitch. Welcome to the group. In answer to your question as to whether you should be "afraid" about your boyfriend's "getting off" on the comic you drew, here is my feeling.
While you are certainly entitled to react in whatever way you wish to your boyfriend's "interest", as I like to call this, of the comic, my feeling is that no, there is nothing to be afraid of at all. We all have our "interests", or "fetishes", and while you certainly have the right to feel a bit "weirded out" by it, my view is that it is more "unique" than anything else, and not weird, and that since we are all unique, this is just your boyfriend's specific enjoyment.
For example, if you notice my signature picture, it is of a barefoot girl on a ladder. I for some reason enjoy seeing girls barefoot on ladders. I do not know if this is because I like to see bare female feet up high, or for some other reason. I have been here for 3 years plus, and all who know me know about my "interest". I am kidded about it good naturedly, and know I am unique, however, my friends on the forum, like me for the kind of person I am, helpful and friendly, and have learned to accept me for my "uniqueness". It seems to me the same way with your boyfriend, as I would call his interest a unique one.
I hope what I said helped, and again, welcome to the group. If you want to chat about this further, please feel free to ask me. Take care, good luck, and I hope we can chat at some point.
Mitch