Can anyone help with a possible cause of my symptoms?

2000 Cherokee Sport 4.0. 88,000 miles, over heated once since I had it. Bad water pump. January 2006

Water in oil started a few months ago. 4 weeks ago replaced head gasket. 900 miles water in oil again. Did not have head checked. No visible cracks around valves, filed the head with fine file. Checked with straight egde. Filled engine coolant. After it was full found bubbles in radiator with engine running. Oh just in case you ask, I did make sure that all the bubbles from filling were gone before starting the engine.

What is the possibility this is a cracked block? Is it more possible it is a warped head as opposed to a cracked head.

Do you guys have past experience with this or similar?