No Carbination

I'm just opening my first brew (honey wheat) that I bottled about 4 weeks ago. The problem is that it seems very under-carbonated. I get the *hiss* when I open the beer, and the beer itself has some carbonation, but it still seems almost flat.

I used 3/4 cup of corn sugar for the 5 gallon batch (as the instructions stated). I boiled that in about 1 cup of water to dissolve it, added to my bottling bucket and gave the beer a few gentle stirs.

Should I have used more sugar or do the beers just need to sit longer? (BTW they are at room temp right now, around 78F)

Also, could the temperature I fermented at play a factor? I had no way of keeping the primary cool, so this ended up fermenting at 78F (probably higher inside the fermenter I assume). Could I have just tired out the yeast?

Thanks for any feedback

Eh, I have one batch that is slow also. It will get there evenually.

https://www.homebrewtalk.com/f39/ever-have-batch-slow-carb-up-143876/

Thanks for the link. Sounds like I'm just going to have to be more patient!