Possible odyssey head gasket

First of all, id like to mention i live in my van, and
travel cross country in her. So, my odyssey has
been acting kinda odd for a minute. The engine
light came on, so I had her codes read at a shop. It
came back as emissions, and they told me it was
an o2 sensor. I continueddriving her afterwards,
figured it was ok. A few days ago, she randomly
would not turn over. I turned her off and waited
about 10 mins. She started up fine. A few hours
later, same thing. She ran fine afterwards for
another day. Then, I noticed her overheating while
driving on the highway. Pulled over, and see smoke
from under the hood. The coolant reservoir was
bubbling, and steaming. We let it cool down, added
water to the radiator. Begin driving again, and not
even a block later shes overheating again. We then
noticed the thick white smoke coming from the
tailpipe that smelled like syrup. Whenever I tries to
start it again, it ran rough, like it was misfiring. If
the van sits idling, it does not overheat. Only when I
drive her for more than 3 or 4 minutes does she
begin getting hot. You can hear the bubbling from
inside the car. Help!!!
We are also homeless and live in the van, so
certain things that might be possible to someone
with resources, we do not have.