Zyrtec and shock

I started using Zyrtec recently after my niece received it from her doctor as the solution to her allergies. (We bought it at the drug store). My allergies are skin related where i walk and feel a deep itch in my thighs and anywhere else i have tight clothing. Also when i work out - i have itch deep skin. This is under the surface and very uncomfortable especially when you are walking/working out. Leads to confusion etc. I had never used any allergy medicine before but decided just to see if i would feel any different.

Anyhow, I started using Zyrtec the other day and almost immediately, I started fighting with my boyfriend - everything i was angry with him about came out. It was helpful but also i was very mean in my approach. I also started getting back pains around the spine area - not in the spine but around it and could not sleep until i took an ibuprofen. Today i experienced left shoulder and back pain. That was it for me and whats funny is that i took the lowest possible doze. So i am not touching that medicine again. I am a 36 year old woman. Its a strong medicine and something is strange with it (changes moods etc). I will have to change the medication for my niece before she goes through the side effects.

Have been taking Zyrtec for about 3 months now, due to chronic hives. Was put on zyrtec after going into anaphylactic shock. The hives are gone but now I have bouts where my hearts flutters and pounds like crazy. Don't know what to do because this is the first time in 5 years that I haven't had hives but am afraid of what long term side effects may be.