If i haven't missed a birth control pill in a year should i be worried about being pregnant?

Yes.: Even with optimal use, oral contraceptives have up to 5-8% failure rate (i.e. Pregnancy). Take Folic Acid 1-5 mg daily and consider iuds instead for a 99% efficacy, after a negative home pregnancy test.

No more than usual: Longer use does not increase your protection. In theory and with perfect use the birth control pill is 99+% effective, and for most women it works quite well. However, even 99% is not 100% (it will fail for 10 women in a thousand) and it will not reach that number in real use because women forget or are late or take medications (like most antibiotics) that interfere.