So i made a mistake.
I tried to use the wrong pump on my tires (i used the schrader side instead of the presta side) and accidently let all the air out of my tires in the process.
(Yes i was stupid enough i did this on both tires, please don't judge too hard).
Now when it comes to pumping them back up, with a presta pump i might add, the valve appears to shut when i put the pump on due to lack of pressure inside the tire, and hence not allowing me to pump my tires up.
Basically, what do i do :'(

Edit: i apologise for poor/incorrect terminology, as it suggests on the side, i'm a newbie...

Loosen the nut on the end of the valve a few turns.

it's been loosened to the end, still not filling up with air

Blow Harder

Does seem strange. Given you managed to deflate the tyres with a Schrader the valve cannot be stuck closed which sometimes happens if it hasn't been used for a while. The Schrader has a little pin in its centre to open the valve when you are pumping things up which will be why it deflated the Presta. The Presta should be clear so that the valve closes under internal pressure. I might only guess that something in your pump fitting is holding the valve open. Since you mention something like a dual headed pump I assume it has the rubber sleeved head. Check that it hasn't suffered any internal damage and make sure it is properly mated to the valve stem, spit helps.

Also, if you push the pump head too far on it will press the nut down, making pumping the tire impossible.

When you push down on the pump handle is air still coming out of the schrader hole in the pump head? Or, are you finding it difficult to push the pump handle down?