The past month I have been refilling my empty coolant reservoir before each trip. 

My most recent trip I noticed every few moments I would lose some performance, the RPM's would stay the same but my acceleration would slow.

I got home to investigate the problem and found the source of the coolant leak, my cylinder head...

Here are my questions:

1. This power loss I am experiencing, is this coolant leaking into my combustion chamber?
2. I called a mechanic who recommended I try to use some head-gasket sealants, is this a good recommendation or have I 'passed the point of no return'?
3. About a month ago, I changed the timing belt and water pump, is there anything I could have done that would have caused the head gasket to blow?