Can I take back a statement I already gave?

A statement already given can't be withdrawn. But two things remain available.

Stop immediately. Whatever has been said, continuing makes it worse. You can invoke at any point, including mid-interview and including after answering questions. The statements made after a proper invocation stop accumulating.

The statement may be attackable. Whether Miranda applied and was complied with, whether any waiver was valid, whether the statement was voluntary given the circumstances and your condition, and whether an earlier invocation was ignored — all of these can be litigated, and they're litigated on the record of what actually happened.

What helps counsel: your own account of the interview, written down while you remember it. How long it lasted, who was present, what you were told, whether you asked for anything, whether you asked for a lawyer and how you phrased it. That last detail is frequently decisive.