Looks like a climbing hydreanga to me. It's blooming too! They apparently take years to settle in. Lucky you!

Beautiful plant!...Yes it is a climbing hydrangea. Looks like the commonly known climbing Hydrangea Anomala Petiolaris.

You should be very happy with the amount of blooms on your plant as this plant is known for taking many years to bloom!!

You need to be aware that this plant, left unpruned will grow into a massive woody vine. I mean massive!! (do a search for pictures of "Anomala Petiolaris" and you will see what I mean) It will easily overtake and possibly damage the structure that it is now climbing on unless drastic pruning measures are taken. Prune it right after blooms fade in late summer because next years bloom buds are formed this fall and if you prune it later, you will be cutting off next year's blooms. Other than that, just keep it nice and moist and enjoy it. Whatever you are doing now seems to be working just fine. It's lovely!!...yg

thank you yellow girl! can you tell me how much I should prune it? how much do I cut off? thank you!!!!!!!!!

I can't see the whole growing situation in one picture but it probably will be a matter of trial and error...Just let your eye be the judge. The goal is to keep it inbounds not to chop it up heavily each year therefore eliminating all chance of blooms. If you have one particular woody branch that is too heavy for the supporting structure or causing it to lean, etc., you can cut it back to the base of the plant.
This hydrangea is not happy to be transplanted or I would strongly suggest that you move it to climb on a strong tree or chimney where it could do it's thing the way nature intended. Still, others have managed to transplant them successfully. Others have successfully kept them on the smaller side as well.

Remember, climbing hydrangeas bloom on the horizontal branches so if you cut them too severely you risk next seasons blooms. It's the vertical branches that become heavily woody.
Your plant (in this photo) does not look threatening at this point and I don't want to give you the impression that your fence is going to fall down tomorrow by any means, but you should be aware and just keep an eye out. There is much written about them on this site. Do a search of this forum for climbing hydrangeas and read about the experiences of others. They can probably be more helpful. Good luck....yg

thank you for all the great info! i'm such a newbie and i'm learning so much here.