Can't let myself be happy.:(

I took a test this morning and got a very faint positive. I'm so afraid it was an evap and that I'm not really pregnant and my AF will be in 2 days. We've been trying for over 6 months for baby #3. I keep looking at the test, 2 different brands, both with positives and convincing myself it's not real. How to I just let go and be happy? For some reason, with both my other babies I didn't stress like this.