The Wild Within by Gwen Martin

Duncan Maxwell’s days revolve around helping others, so when his best friend needs Duncan to drive his younger brother around, he doesn’t hesitate to say yes. A little less sleep is an easy price to pay to improve someone else’s life, and many of Chance’s appointments are at The Collective, where he volunteers. It also doesn’t hurt that Chance is charming, funny, and…attractive.
Chance’s world spirals into a blur of adjusted medications and support groups and therapy appointments after his recent bipolar diagnosis. He can’t complain, though, because most people don’t have the support that his brother affords him. Instead of wallowing in self-pity, he focuses on not being a burden and searches for life beyond his diagnosis—maybe even a life with Duncan.
But while Chance struggles to tame the wildness within himself, he watches Duncan silently push himself past the brink of exhaustion. In his desperate attempts to help find balance, has Chance caused Duncan to destroy his own?