Ok, so a spoke just fell out of my bc wheel then i took it to the LBS and the guy fixed it and tightened all the spokes. So now i am trying to put the tire and tube back on and i know this sounds stupid but i cant pump it up because the valve is too far down. The rim on my wheel is in the shape of a “V” so i guess the valve isnt long enough but it was fine when i got it. I keep trying to pull it back up but it goes right back down when i let go, i have managed to get the pump on there a few times but it keeps blowing off because the valve keeps sinking in the rim. Its really annoying, HELP! 
You need a valve extender. Go to your local Auto shop, like VIP or NAPA and they should sell them. I got mine in a pack of four for $3.
just put the valve cap on the threads after you put it through the rim.
then mount the tyre.
then push your thumb down on the tyre above where the valve is.
take the cap off and have the pump ready and put that on.
pump as much as you can till your thumb cant hold it down anymore.
it sould be fine now, finish inflating the tyre.
ditto.
Yes, frustrating! I feel your pain.
Some valves have a screw collar that is there to prevent this problem. I guess yours doesn’t.
In that case, as the others have said, push it through by putting your thumb on the tyre.
Alternatively, old style pumps had a screw fitting on a flexible hose, unlike the modern push and click type. Can you find one of those?
Persevere.