Why is my boyfriend so uncaring and detached?

Okay so, keeping it short: we went on a college trip, got drunk, kissed a little and one day later he asked let’s give it a try?
And we got into a relationship.
Now, he thinks he got me too easily (he actually said this) and is totally uncaring and detached. Never shows emotions or that he cares AT ALL.
doesn't let me be romantic and neither does he himself do anything even remotely romantic. Nothing sexual either.

(He’s has bad past experience 2 years ago. His ex left him without any good reason and he was heartbroken.)

anyway it has been 5 days since the relationship began
what do i do? Do you think he needs time or what?
Why is my boyfriend so uncaring and detached?
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