I don't need to tell you how difficult caring for a loved one can be. You are feeling guilty for not doing enough, frustrated because you can't fix the problem, tired from lack of sleep, isolated because you don't have time for friends, pulled in many directions and stressed out.
It will take time to figure it all out but asking for help with your loved one is a good start. By asking for assistance from family, friends or a home care agency, you allow yourself the time to get yourself organized. With organization, comes reduced stress.
You won't be much of a caregiver if you have a health crisis or emotional meltdown from the demands of caregiving. Take care of your health; be willing to ask others for assistance whether it be running errands or making meals or helping with household tasks; find out about community resources; hire a home care agency, join a support group; learn to relax through meditation or other activities that will take you to a place that makes you happy or calm; deal constructively with negative feelings and start by learning to forgive yourself for the anger and resentment you feel.
Most importantly, remember how special you are. You have taken on a huge responsibility on top of everything else you do. You are not alone, there are thousands around the world like you and each has a unique situation. Remember, that often, people are willing to help but if you give the impression you can do it all, they will not offer. Most people are just waiting to be asked. Only you can tell them what you need. And once you get that needed help....you might even find that your relationship with your loved one is much better because you are spending more meaningful time with each other.