samdontunderstand

I have a 2012 dodge journey sxt automatic v6 fwd. Weeks ago it started running hot and the.ac/heater wouldnt blow hot cold or hard,and my transmission seemed like it wasnt changing gears as it should, I tried to switch to manual but instead of reading a number to indicate what gear I was in it just stayed on D. after I shut it off a while I put some water in it. It was running fine for about a week then it started overheating again so I parked it. Following day I took it to get an oil change and have them check the fluids.the only thing that they told me was I needed a new battery and all my fluids looked fine. The next day I went to work I didnt have any problems all day. As I loaded up to leave my last job it wouldnt start, I got a jump and started my way home. About 10 miles in my car started overheating on the highway so I got off the next exit and before I can pull over it killed. A friend tried to jump me with no success. I had it towed to my house. The next day I walked with the old battery and got a new one from the store and installed it, pressed the starter and it wouldnt turn over. Got it towed to a mechanic who told me I needed a starter so I had him go ahead and change it. I tried to pull off and white smoke started coming from the exhaust about 2 miles down the street it overheated killed and wouldnt start. After about thirty min it started. I went back to the mechanic who told me I blew a head gasket and there was water in the oil. Also that I needed a new engine. I took it for a second opinion and was told to try k seal. Once I got home and parked I waited 24 hours and read the instructions carefully attempting the k seal method. Also no success ive had different ppl say different things that it could be waterpump,thermostat. I need help.