How does your picture look on analog? If most of your digital channels are on VHF then see how well your picture looks in the 2-13 range. If the analogs look clear then I think the digitals might be coming too strong. If they look bad then you probably don't have an antenna designed for VHF.
I'd try cheap $10 rabbit ears. You want one with the long poles, the poles are VHF and the loop is UHF. I live 21 miles from my transmitters and can pick up all the major channels with a UHF loop. I still use a roof top for reliability though.
Finally it might be worth your time for ota, in Phoenix we have two local stations with HD that are not carried by anyone. One has local Diamondbacks games in HD, the other is just My network Tv but is soon expected to carry the local Suns games in HD.