Virtually all the serotonin reuptake inhibitors have this property. The Imipramine will not cause this problem, but can cause an acceleration in mood swings and is best avoided in any type of depressive or manic depressive illness until other agents have failed. Your moodiness is not mania. Your evenings of poor sleep are not mania. They are just moodiness and poor sleep.
Mania is a collection of behaviors, like depression is a collection.
Mania includes talkativeness, hyper sexuality, spending sprees, decreased need for sleep, aggressiveness, grandiose feelings, etc. You did not really describe these. Hypomania is a lesser amount of these, but I doubt you have that either. The paranoia is probably part of an anxiety disorder if you have anxiety. It can be part of mania, but again, I did not get a manic feel from your letter.