Possibly pregnant.

Okay my period was July 10-14 ovulation was 20-27. And I had intercourse the 26&27 also today was suppose to have my period and nothing normally comes right in time  I've been sick in the morning and bad head aches. But I don't know if it's to soon to tell. Any advise? Oh I am 25 with for children already. So I kind of know my body but every pregnancy is different.....please help