pre-deployment woes

Well we are approaching the deployment day. almost done with the training part and moving too fast towards d day. D had a month long training last month and was injured on his return home. so i have been dealing with that among other things. but since then anytime D went to pick up his car keys or leave the room brennen(who will be 4 in a few month) would say "daddy are you coming back? please dont leave me.." well we have explained that daddy has to go soon and will be back before he knows it. i have continued our normal schedule of play dates and crafts and now going to the pool. it was seeming to work but since he was injured he was out of work for 2 weeks and with in those 2 weeks brennen has become a daddy's boy. well now on to this past saturday night. as i put him to bed and told him to kiss and hug his daddy, since he was going away again for a little bit but would be back. he fought me so hard i had to pat him to sleep. i woke up at 3:30 to take D to the airport(on mothers day) and i had my sister stay with brennen so he could sleep, well he woke up at 4:30am and so did she. when i got back home we got ready for church. of course like always his teacher was late and he was being moved to a different room until she showed up. he had a melt down. "please dont leave me, please mommy" so with those pleas i stayed until she got there and i explained what was going on with him. she said he did wonderfully during the hour i was in church. then we go to lunch. i park the car and get out. i go to his door which is on the driver side and he is freaking out/screaming bloody murder. "please dont leave me in the car" FYI i have NEVER left him in the car, EVER. so i have no clue why he is doing this, but he now does this every time i or anyone else gets out of the car. then sunday night i have to pat him again to sleep and he wakes up hysterical at 5:30am. had a great monday with no melt downs until its time for bed. i have to pat him to sleep again, however this time he only sleeps an hour before he wakes up hysterical again. i finally get him into his bed again at 10:30pm and turn on his tv so he can watch a movie. he has cried out a few times since being up there, but i dont know what else to do. i cant let him sleep with me, he will never go back to his room other wise. and what in the heck am i going to do in less then a month when D leaves for 10ish months. within those 10ish months he will get a baby sister, starts preschool, turn 4 and go through so many holidays to count. ive looked up everything i can think of to try and help him and nothing seems to work. maybe if i stay strong he will stop, but im not sure how many more times i can tell him to go back to his bed without crying myself. its breaking my heart.