The concept of existence is a difficult one to get your head around. It probably seems clear to you that you exist. It probably seems clear to you that your friends and family exist. You’ve never had any reason to question existence in general, and it can be uncomfortable to do so, I assure you.
First, let’s take a look at the people around you, people you share experiences with. Can you really be sure that they shared those experiences with you? You are undoubtedly conscious of the first time you kissed someone, or at least conscious of a time you’ve kissed someone, you remember it. But it is impossible to discern whether anyone else’s consciousness is anything but an illusion; you may, essentially, have been kissing an organic robot that is incapable of experience – it simply follows scripting in a similar fashion to computer software.