I've tried everything I can think of! Please help (Boot issues)

Hey guys,
So I'm a 15 year old and I built my computer almost a year ago now, and now it wont start! To clarify, all the hardware is seemingly functioning properly (fans, GPU, HDD, PSU, ...), and here is what happens when I press the power button...
1. Everything starts like normal, I hear the fans starting up and everything inside looks fine
2. My monitor starts up sometimes as if it is recieving a signal but it still displays "no signal"
3. the indicator lights display a constant: light-light-*short pause*-light
4. I cri everytiem

Things I've tried:
Unplugging cord, holding powerbutton for a minute then reconnecting; booting with and without connected HDD; taking out and reinserting the GPU; and connecting it with both hdmi and dvi to my tv and monitor.

This was my first build so I dont have any extra parts to experiment with... any home remedy ideas or should I take it in and pay for diagnosis/repair?