Your friends need to know what you're going through. They need to understand all that you feel, including anger, frustration, loneliness, hopelessness, anxiety and exhaustion. These feelings are all part of caregiving. There's no benefit to trying to pretend it isn't so.
Reach out if you're lonely. Feeling lonely or isolated as a caregiver is common. These feelings become worse if you don't reach out to others and spend some time socializing.
Even though you express your feelings to your friends, try to talk about other things. Don't disconnect entirely from your life. It's out there waiting for you.
Ask friends to help you with specific things. Maybe you need someone to go grocery shopping with you. You never seem to find time, but if you go with a friend, you'll have some time to chat and get some help bringing in the bags!
Encourage friends to "bug you" to do things with them. Get them to help keep you from isolating yourself.
If you can't get away, maybe you could spend some time in the evening on the front porch with a friend.