Ovulation tests since 

Since 2/26. I keep getting BFN on 

hcg tests. I haven't tested since 3/6. I feel like I have some pregnancy symptoms such as backaches and headaches. Any thoughts? If I am late - how late would I be? How soon can you  take a test to get a positive result.  I'll be 38 in may and i got my 1st AF at 16. We have 32 sets of twins in my family. Faternal and Identical.  I also have gained 5 to 7 lbs but bow only 5lbs.