A few more things to add to what FDS said:
Assuming your plane is straight and square there are two things which either alone or both combined can lead to or increase the likelyhood of the behaviour you described:
- A lack of airspeed will make a stall more likely especially coming out of ground effect on takeoff. Low airspeed will also increase the effect of prop forces.
- A tail heavy plane will be inherently unstable, so make sure your CG is in the indicated spot or slightly forward of it.
Taking off from the ground before you know how your plane will react is a risky endeavour as well. The pietenpol might be light enough in wing loading that you can test glide it without the engine. If you do don't feel tempted to gun the engine and fly out of it. chances are prop forces are going to make you crash. Look for a nice, tall spot of grass to throw your plane at.
I would also suggest the tiny trainer as your first plane before trying somethng more involved like the pietenpol.
You don't even need a kit. Lots of people, me included have built the tiny trainer from foam with the free plans and flown with success.
I've said it before and I will repeat it here. the tiny trainer is excellent to ease you into flying. You can use it as a chuck glider, get comfortable with hand launching, then add servoes and do a few glides down a slope or something and then add the power pod nose and really get flying.
All the electronics that work with the pietenpol will fit the TT as well.
The most important thing is not to give up. Analyze your flight attempts, maybe even film them, share them with flying buddy or the community here. We will do our best to get you into the air.