This is difficult to tell without asking a few questions. But my immediate thought is that you are over training.
A couple of questions:
How often to you train per week?
When is the last time you took at least 5 days off and did some active recovery?
Do you use variety during your workouts? Do you cross train?
Do you train heavy every workout. As in Benching one day Deadlifting the next and then Squatting. All done heavy with low reps?
What is your diet like? Do you eat balanced meals and drink a sufficient amount of water?
Are you feeling stress from work, or a relationship that is not going the way you'd like?
I saved the most important for last. Are you getting a solid 8 hours of sleep every night? Not once in a while but every single night, no less than 8 hours of sleep?
If you answer the above questions we might be able to nail it down for you.