Every month you do this. Symptom spot like crazy.
Yes you have only one tube. However you don't KNOW that it is blocked and you need to wait til Aug before you can go to the docs.
Be honest. You may have more chance if you DTD a bit more often 
And if it is this month.
Be prepared. It has been nearly 13 years since you did this. Your body IS ALLOWED to do a test run
It doesn't mean you've failed. You were 20 when you had DD and you've changed quite a bit.
Every time AF comes it is a clean sheet. A new start.
You could help yourself by giving up smoking
And cutting down on the coffee.
So every time you get disheartened
Come back
Read your own advice.
And take it.