1998 Cadillac Elderado, loosing water from the reservoir but no obvious leak.

What is your question?

Overheats if I'm not careful about checking coolant. Also noticed after running the vehicle, maybe an hour later the reservoir has pressure still on it. Could it be a head problem?

What makes this problem better or worse?

If I don't stay aware of the coolant level constantly

How long has your 1998 Cadillac Eldorado had this problem?

A few weeks