second child guilt...?

so, i just found out we are pregnant with my second child... i am super excited, and i know my daughter(3.5) will love being a big sister. however... i was a single mom up until my boyfriend took on the title of Dad with her back in may/june of this year. hes been with us since jan 2016. but she never called him dad until may... well... now i find myself having guilt about having another baby... she is my world. the light of my life. and my reason for waking up in the morning, even when my depression is getting the best of me... did anyone have second child guilt? im terrified of not being able to love a second the way i love my daughter. but ive always wanted a big family... and i KNOW she will love being a big sister... but im just so scared that shes going to feel betrayed... etc i think i could go forever.. just lookin for other experiences, advice.. anything really.