If you are still having that much trouble playing a C chord after 5 months something is wrong in my opinion. If you think you are doing everything right with your fingers that would point to your guitar as the problem. The action may be too high and it needs a proper set up by a guitar tech. Also an electric (properly set up) is much easier than an acoustice for learning. I would suggest going to a guitar store (even if you don't intend to buy) and pull a few guitars (both acoustic and electric) off the wall and try playing your C, D and G chords. If you can do it with one or more of those guitars that will show you if it is your techinque, or if your own guitar needs a set up adjustment.
[Epiphone Les Paul Standard Plus Top Pro (2), Fender Player Stratocaster (2), Fender Player Telecaster (2), Squire CV 60's Stratocaster, Hamer Ecotone, Yamaha APX600 (2), Epiphone ES-339, GTX-100 (2), Spark 40 (2), Spark Mini.]