DS is 5
Around a month ago he started clinging to me constantly. At school in the mornings, when I go to work (he is either with DP (who is his dad) or my parents) even if I have a shower. He will not let go of me and has to be peeled off, while he sobs and screams for me 
He has never been like this before and it's breaking my heart. I've spoken to him to see if anything is wrong or bothering him but he says he just loves me and misses me when I go.
I am bright and breezy when I go, kiss, cuddle and "see you in xxx" but, once again, I have left a snotty mess with DM so I could get to work 
Is this a common phase? I've checked with his teacher and she says he's fine after a couple of minutes, my Mum says the same but I feel dreadful every day 