Yes, this is most likely an ERISA plan but the DOL isn't your recourse here.
If by "hard time" you mean they have rejected your claim for benefits, then the first thing you need to do is file a written appeal with the carrier. Information on how to do that must be provided somewhere in your insurance booklet/plan document. If they still believe you aren't entitled to payments, then your next step is to file a written appeal with your State's Insurance Commission. If you are still denied benefits, then you can sue the carrier. You might as well exhaust your free options first though.
You may always consult with an attorney at any point as well.
Without knowing the details of your medical situation AND the fine print of your LTD benefit, particularly how they define "disabled", it's really not possible to advise you further. The definitions in some plans are highly restrictive, so it's possible to be disabled and still not qualify for benefits. There may also be some interplay with social security disability benefits that you need to factor in too.
Good luck.
