Product: Student loan

I graduated from XXXX  XXXX University in XX/XX/XXXX. At that time I consolidated all federal loans into XXXX loan with a total of {$21000.00}. After graduation I continued to defer my loan until I was able to set up a repayment plan. In XX/XX/XXXX I XXXX XXXX to my XXXX  son and unfortunately lost my job. I was out of work and a XXXX  mom overwhelmed with life and unfortunately neglected to continue deferment on my loan. This caused my loan to fall in default. In XX/XX/XXXX my husband filed his taxes, and without my knowledge there was an offset on my name due to the past due student loans. This caused his tax return to be held which was {$10000.00} ( unsure of exact amount ). Upon figuring out that it was caused by my student loans, we were advised to file a Injured spouse form. This is because the income was my husbands and not mine. After a few months the IRS returned his tax return. I notified the IRS to find out what to do to fix the issue. They advised me at that time that Navient had been the one who had the offset placed on my name. I contacted navient in XX/XX/XXXX to rectify the situation and bring the account into good standing. I spoke with a rep at Navient and explained my situation, they told me the amount of my outstanding loan to be {$17000.00}. Unfortunately I did not have any prior paper work stating my actual student loan amount that was consolidated in XX/XX/XXXX. I knew I had about {$20000.00} so when they said {$17000.00} that seemed correct to me at the time. The rep stated I could apply for the income based repayment plan and because i had XXXX  income I could be approved for zero payments. I did the paper work and the account was placed on the Income based repayment plan for 1 year with {$0.00} payments. After a couple months I started receiving two different bills from Navient. One bill stating the zero payments due with a balance for {$17000.00} and one stating the loan was past due with a balance of over {$30000.00}. I spent months on the phone and computer researching and trying to figure out why I was getting two separate bills from the same servicer with two different amounts when I should only have 1 loan. 
I graduated in XX/XX/XXXX, I consolidated all my loans in XX/XX/XXXX, I have not been back to school since so why do I have an additional loan that has a disbursement date of XX/XX/XXXX which is when the IRS took my husbands tax return. When I research my loan from XX/XX/XXXX, I can account for each semester that loan paid for and it totals exactly what I borrowed during school. Where did I spend an additional {$17000.00} on school? I have spoken to Navient more times than I can count and they are never able to help. I have followed all steps they have asked me to do as far as sending in a certified letter explaining the situation as well as documentation of all money used. I never heard back from anyone. They continuously push for me to consolidate the two loans together which I refuse to do. I have also reached out to several lawyers, but unfortunately there are not many that handle these cases in my area and I am not financially in a position to fight against such a large corporation. I have been leaving them alone because I am scared of what to do and they have advised me incorrectly I feel in the past. My loans are getting ready to go in default again and I want to prevent this from affecting my financial future. Please advise me what to do or how to handle this situation. Thank you for your time.