Think I’m pregnant again

I gave birth to my baby girl 4 months ago and I think that I’m pregnant again! Me and my partner have been together for 3 years and my daughter was planned after I had miscarried just before I fell pregnant with her. Me and my partner have been using protection and I have booked a doctors appointment to have the coil fitted cause I’m 100% sure I don’t want another baby just yet ( although I do absolutely adore my baby girl I want to enjoy her life first) so I have been feeling extremely nauseous so I took a pregnancy test 2 days ago and it was negative but I was supposed to come on my period 3 days ago and I still haven’t come on so I’m freaking out as these where the first signs I had when I was pregnant with my baby girl! My partner keeps telling me if I am pregnant he doesn’t want to get rid of it but I don’t think my body can take it again so soon ( I had a lot of pregnancy problems and ending up giving birth 2 weeks early because of this) I’m so lost on what to do cause deep down I wouldn’t want to get rid of a pregnancy but I would struggle so much 😩 anyone else been in a similar situation just need some guidance 😪