baby fever

so yes I have baby fever badly I got a 5 year old and an almost 2 year old, my fiance and I talked about having another baby so we been trying idk if I should talk to him about preseed or not, I been trying everything to get pregnant the legs in the air over my head on the wall taking prenatals my oldest son told his grandmother mommy is going to have a baby, ok weird as it sounds my fiance has two kids from a previous relationship she passed away of cancer my oldest son said he seen her down in the basement mind u we didn't talk about her around him at all he knew her name picked her out in a picture when we showed him and said mommy pregnant a month later found out i was pregnant with my almost two year old, I been throwing up on and off, I bled a lil bit for one day now it's like a pinkish color and I'm having cramps just a little bit, I wanna be pregnant so badly i even have dreams about it my fiance says just let it happen but am I wrong for wanting to try preseed?!