well OID can get tricky as the name says its ORIGINAL issue discount. amortization of the difference between the original issue price (which is at a discount) and redemption value. OID reported may not be correct if you bought the security in the secondary market. since as stated it's may be figured on the original discount not yours.
see this IRS pub
https://www.irs.gov/pub/irs-pdf/p1212.pdf
to the price you paid you add each year's OID which is supposed to be reported on Schedule B as interest income if held to maturity and the OID is correct there should be no gain or loss. if sold before maturity you could have a gain o loss.
