Congratulations on teaching yourself to knit!!!
Do not worry. What you are experiencing is normal for new knitters.
1) You will become more comfortable holding and manipulating your needles over time. You will also, no doubt, evetually try different types and brands of needles, finding the one that feels best to you.
2) What you are experiencing is tension problems, which happens to all new knitters, and even some seasoned ones. Sometimes you're too loose, sometimes you're too tight. Rest assered, practice makes perfect (or at least close to it). Again, time will improve this, but your tension can change with the project, yarn and needle, so you will need to (and learn to adjust) on each project you do.