Seperation Anxiety????

What is that? I ask myself. I have never experienced that with any of my kids before. They have all been really great to start school, nursery, have sleep overs at grandparents house, have babysitters etc. etc. I used to think when I would see kids freaking out when their moms would leave "you obviously need to leave him more often". Judgmental, I know. Well, I no longer feel this way. Out of the blue my little guy has started having this "seperation anxiety" as everyone calls it. I don't know where it came from and why because he has gone to "daycare" at the gym since he was less than a year old, gone to nursery, had sleepovers with family, etc. etc. all without ever a word of complaint or sadness. He has always "LOVED" having babysitters. I think because they eat whatever they want for dinner and have dessert and stay up late. Anyways, he has recently started "freaking out" when I drop him off at preschool. It is the weirdest thing. He lOVES preschool and ususally doesn't want to leave when I pick him up when its done but for some reason unknown to me he HATES it when I drop him off.  There are no problems at school, he is not being bullied or bored or challenged. He does just fine when my girlfriend takes him on Wed.'s becasue I have to go to work earlier and last weekend when I was out of town and Travis took him he did just fine! So, it has to be a "mom" thing right? This last Thursday when I took him I tried everything. I tried sitting down and playing with him for  a little while, I tried bribery (great mothering skills I know) I tried being very stern and spanking him (wow, 2 thumbs up for me), I was lost and fresh out of tricks. Nothing worked. He would get brave and say he was going to be a big boy and just as we would start to walk in he would stop dead in his tracks and freeze. I had just about had it and had a million things to do while he was in preschool so I decided to just take him with me. I went inside to explain to his teacher the situation (this has happened the last couple weeks, so it was nothing new) and she advised me to not take him. She didn't want a pattern to start where he thought he could just go with me anytime he didn't want to go into preschool. She assured me that he cries for about 5 minutes and then he is happy, smiling and has a GREAT day. She said if you want to bring him in and just give him to me crying or not and if he doesn't stop in 10 minutes I will call you. So, I did. He cried, grabbed my neck and shirt and had to be pryed off of me, I think I even had a scratch on my neck. Quite tramatic. I left feeling horrible. Then I headed to the older two kids school to pay for lunches, take forgotten homework and bring Ally her violin so she could play for her class. It wasn't more than 3 minutes I got a text that he was happy and having fun already!  Oh brother, was my thought. All that drama and you are happy already? So, some may say, why even have him go to preschool if he acts that way, its not like he's in regular school yet or anything? Well, he LOVES it, he really does. Once he gets over me dropping him off he has a great time. He talks about it all the time and the days he doesn't go he is asking if he can. Being kind of like an only child during the school year because he is so much younger than the other two he really needs to have something to do, as do I, ha ha! I decided to try a "treasure box" idea. I got a bunch of cheap little toys, candy, etc. and put in the "treasure box" and every day he goes to preschool without crying he can come home and choose something from the box. Here's hopin! Anyways, it is so bizarre and I am not sure where it is coming from but boy do I hope it passes soon. I really don't want to be the one to have the kid in kindergarten that has to walk her child to the playground and wait for the teacher to get him every day!!! I