Won't sleep unless in swing

So my.son is 4 months. We have been having trouble sleeping. Which I know is normal at this age. At night he sleeps fine in his bed.But during the day he will only sleep if we are in the car or hes in the swing. He use to hate the swing and now that's his only way of napping. I know they say it's bad to let them sleep in it. But I turn it slowly off when hes asleep and I'm never leaving the room while hes sleeping. But is anyone else having this issue?