Maybe you're bored with what you do for work...it's easy to get careless when you're not really mentally and emotionally "engaged" in what you're doing.

How old are you? Hormonal changes can wreak havoc on concentration but so can mental health concerns (anxiety, depression, etc.)

Have you been to the doctor to get a thorough work-up?

If you see a pdoc and or T, have you told them about this recent difficulty? Meds (if you take them), can cause that sort of thing - especially if you're going up or even down on dosage.