This information is general in nature, and not intended to be advice, medical or otherwise. I have a high-need toddler. At 21 months old, my son has finally become comfortable staying with someone else for a time while I run errands, meet a friend for lunch, etc. Even his father could not take him away from me without hearing him scream. When he was an infant, it seemed selfish to put my needs ahead of his, so I didn't.
Life is still only tolerable at best.
But don't despair. Meanwhile here are some things that helped me cope. It will give you insight into your child and practical ideas for coping. Go faithfully to your local LLL meetings for support. Daily phone contacts with women I have met at meetings with children of similar temperaments helped me keep my sanity.