Does using lubricant inhibit conception?

Maybe. Most lubricants - k-y jelly, vaseline, water-based lubricants like astroglide, and even natural substances like olive oil or saliva (spit) are all toxic to sperm. Having said that, many couples get pregnant using these - it may make more difference if the male partner has a low sperm count. Less lubrication may be needed when a woman is ovulating. Pre-seed is safe for sperm - search online.
Yes. The best lubricant is olive or mineral oil. Water based lubricants can be a problem. Use them sparingly.