Feeling lost

There are many times in a parent's career that they feel lost, unsure of what to do next. I am going through one of those times. T is struggling so much emotionally right now, and I have no idea what to do to help him. He is going from my sweet little boy, to an angry, mean kid in seconds. He goes from being my happy go lucky kid to a puddle of tears and shakes in the blink of an eye. It's like someone flips a switch on him, the change is that quick. There are a lot of transitions happening now, the end of preschool, saying goodbye to friends, preparing for summer, and then kindergarten. He's going through a growth spurt, so his emotions are trying to grow with him. He feels out of control of what is happening to his routine, to his body, and emotionally. You can see fear in his eyes when he's angry, as well as when he's sad. His anxiety is palpable at times, and it breaks my heart. Last week I spent an hour trying to comfort T as he sobbed in my arms. He was missing my grandmother who died 1.5 years ago. They weren't super close, but her death is the only experience he really has with losing someone. As he sobbed, and shook, I held him and tried to comfort him. I could feel his pulse racing, and hear the panic in his voice as he asked question after question about his GG and how he could ever talk to her again. His sadness and grief had turned into a panic attack. That was the night that I realized I was helpless, that I had no idea how to help him. Until this week he has been holding it together at school, and then coming home and losing all control. Today, however, was a different story. He went from smiling and laughing on the bus to crying and screaming, and back again with no known cause. He was super emotional during school, asking for me, for his "Geego" (security blankey)and his frustration level was super high. When he came home, he was sweet until I had to say "no" the first time, then there were tears, thrown toys and stomping feet. When he calmed down from that he cried and cried about how he wouldn't be able to take his bird with him when he was a grown up and moved out. Those are just a couple examples of what life for T has been like the last two weeks or so. Granted, he has been able to appropriately handle his emotions during school until today, but he is obviously miserable. And I, his mom, don't know how to help him. The fact that he is struggling so hard to hold it all together through school, and now having trouble with that, makes me very nervous for kindergarten next year. Will he be able to make friends even if his emotions get out of control? Will he be able to handle full day kindergarten? Will he be labeled "the bad kid," or the "baby." I am scared for my son and I have no idea where to turn, what to try, or what the answers are. Today I am lost.