You have 2 yrs' seniority and can't hold a line as a 737 FO? How is that possible? (I'm west coast based, but I would expect Sewark to be very junior in most equip/seats). The junior lineholding EWR 737 FO in Dec was seniority number 12414. Once you get to 12100, it looks like it'd be hard to not get a line. What are you asking for that you can't get a line? That's your problem - you're bidding for the unpossible.
That's kind of like me asking why I'm not getting awarded 787CA - I have it listed for any domicile at 100% on my vacancy bid.