Charlie crash lands on a pre-contact world and has a run in with the locals whose population had been decimated years before by a widespread plague. Charlie, pragmatic as he is, doesn't hesitate to offer himself for sex in exchange for supplies and shelter but in the process makes a startling discovery. Not only are their two species capable of progeneration but their fertility rate is off the chart. As a result, the smuggler spends his time as a veritable baby factory for his 'hosts'- his body so feracious that every pregnancy results in multiples.
The turn around is fast, too. Gestation barely takes a month despite the size and development of the children seeming to be the same as a human's and Charlie's hosts don't give him time between pregnancies to rest. The moment he manages to push out one alien's litter another steps up to take his turn and impregnate Charlie.
They all seem in awe of him and distracted by his rapidly swelling belly though he may be, it doesn't take Charlie long to realize that normal pregnancies for this species last far longer than his and only rarely result in more than a single child. To them he's like a miracle dropped in their laps to help repopulate their species and this is reflected by the way they treat him. Besides keeping him permanently knocked up and on his back either pushing out more young for them or feeding the ones he's already birthed from his newly engorged tits, Charlie's hosts cater to his every need. He has what he's come to think of as 'handmaidens' that help him feed the young and also take care of him. They also give him a special herbal concoction he suspects is responsible for how relatively easy his births are as well as his fast recovery.
He gets used to it, after awhile, and stops trying to figure out how to get his ship running again. His hosts aren't technologically advanced enough to help and while Charlie can manage a patch job he's no engineer so it's well beyond him to fix. He makes peace with his new life and actually comes to enjoy it, especially as his hosts, who previously only mated for the purpose of procreation, start coming to him to experience the pleasures of sex as well. Mating with his already pregnant body seems to be quite the illicit thrill for them...