Should I get a blood test?

So I'm 7 days late on my period and I've took 3 tests already and I'm still getting negatives. If I am, I'd be 4 weeks along. My period has always been 28 days and accurate. My 2 female roommates have already done and had their periods this passed week. I know it differs know some women with the HCG hormone, but it's driving me nuts! I remember my sister telling me she didn't get a positive till 7 weeks. And honestly, I don't think I can wait that long! Especially when I could be starting on my prenatals, eating healthy, and all that good stuff! I don't want to, but I might just have to break down and go get a blood test done tomorrow. My mom and BF think I'm overreacting. Should I get a blood test done and prove them wrong or just wait?

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