Would i know if i had an abscessed tooth?

Yes and No: If the tooth dies violently with pain and possibly some swelling yes however many times teeth die quietly and you would never know unless it was found on an xray. Even teeth without fillings die. Don't stress it/worry about it until and if you need to.

Not always: Some abscessed teeth do not hurt at all and slowly eat away at the jawbone. In other more acute cases abscesses can really hurt and can spread quickly

Not always: Often chronic infections fester until all of a sudden they flare up with pain and swelling. I have seen chronic infections, unknown to patients for years until they become acute or are discovered on x-rays. That it why it is so important to get routine dental exams and x-rays.