Dissociative personalities?

I slip into different personalities when dealing with different situations and people. My behaviour and tone changes automatically. I have extremely deluded expectations and sense of self when coming to social interactions and thus they make me very stressful and avoid people. But isolation is equally miserable. In privacy, I'm a different person all together and if I don't express whatever self comes about, I feel extremely repressed and robbed of my life. I also have extreme difficulty in articulating speech, reasoning, memory and narration in real situations in real time. It's very muddled up. Surprisingly, in private, with all space and time in the world, my logic and writing is pretty strong. I'm 25 now. Unable to do any productive work as I'm constantly tormented by compulsive thoughts of past failures, inadequacies and situations and feel it's too late now. I don't know how to approach for a solution as it's extremely complicated and overwhelming. Thanks.