i start skyrim up and play through helgan then i decide to download some mods. now for some reason i can't attack normal in first person mode. i dont know if its one of the mods or what?

Welcome to the forums but this is hardly any information for anyone help resolve.

By the way where is helgan?

Based on what I've read here, you'll probably have to un-install your mods, see if the problem is still there and, if it isn't, start re-installing the mods one by one until you figure out which one is causing it.

How do you know you are using a power attack - is the stamina draining each time you attack?

the stamina isnt draining but it has the speed and animation of a power attack, also it only happens in first person mode

Wow - you're getting free power attacks!? Endless free power attacks? Are you sure you want to fix this...

Sorry I can't be of more help, I'm on xbox. Hopefully one of the PC gurus will chime in soon.