You meant you are on Day 40 of your cycle, Day 1 being the first day of your m? It depends what day you ovulated. If you ovulated on Day 30, it's still too early to test! Also, you have to buy EARLY pregnancy test. How long have your cycles been in the past?
These tests are 99.9% accurate
Don't get frustrated yet. I figure trying to conceive isn't something that you can rush into. It needs planning and plenty of patience. Being slightly disadvantaged on age doesn't necessarily mean that you are hopeless. People get pregnancy in their 40s (I'm not saying you are 40). More importantly you should keep a healthy lifestyle for a good health.
Being too nervous can delay your menstruation. If you ovulated normal as in a 30-34 day cycle, you should be able to test positive now if you bingo.
Try to relax over the weekend and see if that help. If your m still doesn't come next week, you should visit your doc. I'm sorry I can't help much here.