I'm scared I can't get pregnant

Ahh, this is so like me to over think things! I honestly have no reason to believe I can't get pregnant other than the fact I have this horrible gut feeling. My fiance and i have only been trying for about a week and so I'm just being over dramatic. He is also 45 and I'm scared at his age brings birth defects... Anyone else get this feeling but got pregnant? Positive thoughts :)