I single side fed for about 3 months, and then also seemed to notice that maybe DS2 wasn't getting enough, so I kept him on one side as long as possible, and then offered the second side. However, I have noticed that if he hangs on long enough, I may get another strong letdown, so your body may produce enough for your LO.
Your DS is also probably due for a growth spurt, so he just might be sucking extra hard to get enough milk
and your body will adjust. I don't think it's a bad idea to offer your LO the other side, just make sure he's been on the first side long enough to get the hind milk.
Anyway, those are my two cents - maybe someone with more authority can offer you more sound advice