When should I test?

Hello everyone! My period is supposed to start in 7 days meaning I am 7 dpo. My boobs are sensitive to the touch but not painful as other woman described. This is one major symptom I thought was weird because this never happens to me, even before my period. On 6 dpo I had morning sickness. I only vomited once and then immediately felt better after. I am really gassy and I feel slight cramping from time to time. Is it possible that I could be pregnant? When should I start testing?