Good day. i masturbate often while watching porn and recently i have been very aroused by incest. is this core to a serious problem in me?

It can: yes it can you need to take your mind off this and stay busy doing something more productive. your imagination taking you to a very forbidden area, and dangerous as well, even thought you are not acting on it, but letting yourself aroused to these situation is not a good sign. you are a young man, you have your whole life ahead of you sex is a very small part of our life. keep your mind busy

The more your: orgasm is paired w/any trigger, in this case incest porn, the more the link is created between them. This is called "reinforcement" in behavioral psychology. Please avoid looking at this and focus on other ways of expressing your sexuality. Peace and good health.