When to test

My husband and I have been trying for a rainbow baby for 5 years now, lost the first one the week I found out. He told me he just has this feeling that I'm pregnant this month, I'm scared now I'm reading into everything. I'm 4dpo, cycle should start the 20th or 21st. Kind of feel different, tired, nipples are sore and have been a little harder than usual. Again, I'm scared I'm just reading into things. Has happened before and wasn't, but he has never said he felt it before. When would be the best time to test before 20th/21st? The wait is going to drive me crazy! Thanks in advance for the help.