Overheating/No heat

I’m not sure what else to do. I have replaced the
thermostat, radiator, water pump and the heater
core in hopes that it would help. It hasn’t at all still
no heat and I’m almost positive that my car will
over heat yet again once summer comes back. I
have checked the fuses and they are fine but I
haven’t checked my relays yet about to do that.
Was hoping someone could have another idea as
to what it is other that the head gasket as that will
be my next investment.