can you guys suggest me???

After graduating from the college I joint Consultancy to avoid 90 days of unemployment. While going though training process, I was applying for  full time position as well. After 5 months I got call for full time position for an interview   and cracked it. Now they offered me the position and I am joining next week.  
On my resume for the full time position I didn't mention the Consultancy name..
what should I do ?? should I mention the Consultancy name?? If i don't ...on paper it looks like i am unemployed for 90 day..that means i am illegal on paper but i am not!!! or should i me just be quite and not mention it..But in paper work I think we have to mention previous employer. 
If full time employer asks..why didn't you mention your previous employer name...what should i say?? 
how do i deal with Consultancy ???  
 

suggestion will be highly appreciated. 

For the 90 days unemployment things, it doesnot have to be active job. You can maintain it even if iyou are volunteering or self-employed.

I hope you informed USCIIS within that 90 days. The employer ( to be ) will not search for your work history if you do not mention anything abt your past experiences. The only thing they need is your valid work permit which would be valid if USCIIS was informed within that time. If they ask about your work record for those 5-6 months, you can tell them you were self employed.
If I were you , I wouldnot tell them anything about the consultancy.