There fixed it, you can find it in my profile as 'why can't nothing fly (fixed)'

Check your centre of mass (CoM) and centre of lift (CoL), you want the CoM slightly in front of the CoL, yours is backwards so your engine pulls up, then the wings lift and the mass drops the tail causing an upward tilt... If CoM comes after CoL you'll find the engine pulls up then the plane's weight pulls down (but doesn't cause tilt) the wings will always generate an upward force, if it's too far forward it will tilt your nose up (causing a stall) if it's too far back you'll find it lifts the tail (causing a dive -this is your problem, also your CoM pushes the nose down) also remember that although you take off full power you don't need it for Straight and level flight (usually at 75%)

A note about the centre of thrust (CoT) it will emphasise any imbalance. It pulls forward so imagine in your case the CoM drops the tail and suddenly it pulls you up. If CoM drops the nose (too far forward) then the CoT pulls you down.

Also you don't have horizontal stabilisers which means you can't control your pitch (you could also add this control surface to your main wing)

Hope this helps
P.S CoL is blue, CoM is red and CoT is yellow.