He is doing this to "fill a void" somehow, it's a compulsive behavior that he practices to try to "ease his stress". It's just an attempt to have a sense of control somehow. This is filling "his" needs and he is clearly not even thinking of "any" of your needs at all. Sometimes, these patterns can actually be due to bipolar, not always, but sometimes as in a manic phase a person can actually go out and spend money irresponsibly like this. However, this can also be a sign that the individual is actually overwhelmed with stress and is trying to self reward in an effort to combat the stress they are under.

All of these things you have expressed should be shared with a therapist, so "you" can understand what you are dealing with and how to best protect "yourself" instead of being hurt somehow. It can be painful and confusing to watch someone behave this way, I have lived with that myself and it was very hard on me. However, my husband handled it with turning to alchohol, and while he eventually did stop, it took him a very long time to grow up and learn how to manage himself better. I call these stages he goes through Dr. Jeckle and Mr. Hyde. I have learned that when Mr. Hyde comes out, there is nothing I can do or say that stops this mindset.