It's my guess that something has happened to cause him to be more anxious. Have you had any changes such as a pregnancy, separation, move, fighting, job change, child care change, someone dying, that sort of major thing? Or some change that feels minor to you but not to your baby? Has he seen or heard a scary TV program or movie?
Has he been cared for by someone besides you and is it possible that he witnessed or was a victim of something that increased his anxiety?
Often our babies are strongly affected by situations that we take for granted as being OK. Your son is totally dependent on you for his very life. Because of that he has the ability to sense things that we might not.
The way that I would handle this is to give him the attention he needs. Take him with you when you leave the room. Don't wait for him to cry. Hold him when he asks and when he doesn't. Include him in whatever you're doing. Perhaps put him in his high chair near you while you're doing the dishes or the laundry and then talk to him.
You won't be spoiling him when you give him the attention that he needs. Since this is new behavior he is telling you he needs reassurance. Once his sense of security returns he'll stop most of this behavior.
It's a good idea to cut back on your housework for a short period of time so that you can give him extra attention without feeling stress yourself. Your baby's healthy development can't wait. The longer you try to ignore him the harder it will be for him to return to his more easily to get along with self. Housework can wait for another day..
I went to your profile and noted that you don't have a bedtime schedule for your 2 yo. Toddlers feel more secure when they have a routine. Perhaps making a routine in which meals, naps, and bedtimes are close to the same time everyday would help. Consistency provides security on a physical level.
Later: I agree with Corie and the other posts. This is most likely normal separation anxiety. I must've been in my somethings wrong mode that night. Sometimes my past experiences rise to the surface. :):)