K.L.
I would say he is not getting enough sleep. It does take a child some time to adjust to change - such as sleeping in his own room. Give him time and things should get better.
The crankiness I am sure is because he is tired. The clinginess is something that will subside with time. It is partially because of the age, its just a stage that will go away, but also because of the newness of sleeping on his own.
I recommend setting aside some cuddle time throughout the day. Some special "Mommy and Me" time - maybe before bed - when just the two of you cuddle and read books or sing songs, etc.
I also suggest occasionally having a babysitter or mother's helper to play with him, maybe take him to a playground to he can learn that you are not the sole source of affection and attention. Along with that, I also recommend encouraging some independent play time - that is not saying that you put him in a room alone and ignore him, but maybe you could flip through a magazine and let him learn to entertain himself for a few minutes here and there. Are you a part of a play group? Social interaction is a very important piece of development at this age and it can help Connor to gain some independence.
Develop a routine before nap and bed - books, a video, bath - whatever works for you. When these "cues" happen Connor will associate them with nap/bed time. Stick to it and be patient, adjustments take time.
I know that was a lot to take in, but once I was on a roll...anyway, I hope this helps. Good Luck!