Earliest possible signs of pregnancy?

Hello…… I have a 6month old daughter, and believe i am pregnany again. my period is not due for another week and a half, but i feel nausuas, cramping, and having alot of headaches. if i am prego i believe im about 4wks. is that too early to honestly experiance prego symptoms??? can u see sighns earlier w/ second pregnancy??? what if you were having twins???? my boyfriend swears im prego he just says he can feel it. so yeah basically whats the earliest you have experianced signs of pregnancy???

with my 3 year old i knew i was pregnant a week before my period i had sore breasts and never get them before my period,
i had no other symptoms and my midwife i had for my 3 year old said it was to early to be sure but a week later i got a BFP keeping my fingers crossed for you

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