Baby is 6 weeks old...I think i might be pregnant...

Please no negative comments. My fiance and i had sex about 3 weeks post partum (i was feeling great and all bleeding had stopped) well with me having been pregnant before which is nine months and he didnt have to be careful so long he forgot to be careful and im sure you can assume what happened. I am not sure about being prego it may just be late nights with my baby girl but i am feeling nauseous and ridiculously fatigued no matter how much sleep i get. Im not worried...if i am prego it will be another baby for us to love and spoil however im not sure how it would be with babies so close together.