How to avoid pregnancy after 3-3.5 months of sex

How to avoid pregnancy after 3-3.5 months of sex I had sex with my girl friend 3/3.5 months ago , I did not discharge sperm, but still I am worried if I couldhave some premature ejaculation then there are chances that my partner might get pregnant, I have no contact with her after that incident, I hope she had take her care and taken apregnancy test after that as she is aleady a matured 26 yrs old girl. I am afraid if she had not done that .....,Is there any way that girls can prevent pregnancy even after 3-4 months of pregnancy. Although I didnt discharged sperm still I have fear that if there is any premature ejaculation then it might be dangerous. Pease help.