ohhhhhh dear
What pedals/shoes are you using?
Your oing to have to learn to do it properly, you dont pull with your legs for obvious reasons. Do the following whilst rolling arround at walking pace, a slight downward slope helps a bit.
Crouch low
Pull up on bars and push your feet forewards towards the front wheel, throwing your weightback
with a little practice you should be able to manual (like a weelie, but standing up and not pedaling). You dont need to be able to keep the front end up, but get it as fas as you can, might help if yoursoemwhere soft like a field so you can fall off the back a few times wihtour hurting too much.
To do the rear ride allong and angle your feet forewards slightly. Crouch down and do the opposite what what you did with the bars. Spring up and pull your feet back slightly to lift the rear wheels. As you get better you should be able to get the rear wheel quite high.
Now combine the 2, start off aiming to hop both wheels over a twig at walking pace (i.e the foront is already on the ground when you start ifing the rear. Then build up the speed untill your doing it in one fluid motion. Think of it as riding the bike over an invisible hump-backed bridge. Whereas previously SPD’s were lifitng you over the twig like a forklift truck (i.e. both wheels remaind just about level).