Thank you for contacting JustAnswer.
I'm sorry to hear that you are having a difficult time. One of the most important things you can do for your son is to be sure to not use him as a pawn in your divorce. He should not be given negative messages about either parent and should be allowed to love both of you. Keeping a low conflict level between yourself and his father is also very important for your son to feel safe and secure. The best book on this subject that I can recommend is Helping Your Kids Cope with Divorce the Sandcastles Way http://www.amazon.com/Helping-Your-Kids-Divorce-Sandcastles/dp/0679778012
You may notice some regression temporarily which may include temper tantrums, potty training issues, being clingy etc. However, these should only be temporary as long as you and his father remember to not put him in the middle. If you do see behavior problems, you can also work on positive parenting. Keep in mind that any behavior that gets attention is likely to continue happening. It has been called the law of the soggy potato chip in that if a child thinks that he has a choice between a soggy potato chip or no chip at all, he will choose the soggy chip. If your son feels that he has the choice between negative attention or no attention at all, he will choose the negative attention and so he will act out until he gets it. The only way for this pattern to stop is to begin to catch the good behaviors and reward them with attention, and to calmly and matter of factly give consequences for the negative behaviors with as little attention as possible. A very good book on this subject is Win the Whining War & Other Skirmishes: A Family Peace Plan by Cynthia Whitham MSW. The more consistent you are with this positive parenting, the more secure your son will feel and the more his behavior should improve.
In the meantime, remember to work on taking care of yourself and give yourself permission to be happy and healthy. I hope this answer is helpful. Please let me know if I can clarify further.