will i face criminal proceedings? or if i admit will i just have to repay them money back?

please could i have some advice. ive had a letter from hmrc on my doorstep saying i have been claiming as a single person instead of joint. Im not going to lie on here, i have falsely been claiming benefits as a single person. we moved in together in oct 2011 and i would never think of doing anything like this and it was my estate agent who told me to do it. he told me to do the house application in my name so i did. after i signed he told me as i was down as a single applicant i could claim 25% discount on my council tax a stupidly i did! it then spiraled from there. i told hmrc i was a single mum and claimed tax credits. in april 2012 i renewed as a single person. i have also been claiming housing and council tax benefit as a single person for the whole time. when i got the letter i panicked and rang them i stupidly made up a story. i told them he moved in oct 2011 and moved out mid nov 2011 i then told them he stayed over 2 night a week to see his daughter. i said he moved in permantley in oct 2012. they said they had evidence he was living here the whole time. we have a joint account which we had before we moved in together and he opened a bank account at the same address as me. i just dont know what to do. they said i need to provide evidence he was living somewhere else and all i have is his tax return to april 2012 for his mums address. should i just come clean? if i do will they tell housing benefit? i could handle paying back to hmrc but ive heard housing benefit normally take you to court and i dont think i could handle it. im not claiming housing benefit anymore as on oct 2012 im really scared and i know ive done it to myself and there is no-one to balme but me. its making me sick and i cant sleep. Please help