I'm married for almost 18 years now. My husband suspects all the time that I'm either cheating on him in any way possible. If I talk to any male however younger than me then also he abuses me. At first I took everything thinking he might change and start understanding me and trusting me but now when our son is 15 years old and still these kind of allegations. It hurts me like hell.I love my husband a lot but don't know how to tackle the situation

By staying with a husband that abuses you, you teach your son that this is how men act. He is learning it is acceptable to mistreat women and abuse them.
Is this how you want your son to be when he is grown?

Leave him.