Dada is phonetically easier for them to say. Don’t worry!! Honestly he is not doing to hurt you or because he loves more one or the other! 😙
They often start with dadda as it’s an ‘easy’ sound to make. It doesn’t really mean anything and often when they start babbling they have no idea what they’re actually saying as they don’t associate the word with a person for a while x
My LO says daddy all the time. He’s said mama maybe once or twice. It does look hard to say - when he has said it he looks like he’s struggling! They’ll get there mama. And tbh sometimes he just says dada all day long I’m not sure he’s necessarily referring to his dad or just saying it so I wouldn’t worry
Please try not to worry, they will say mumma eventually. My youngest doesn't really say 'dadda', so its the opposite for us. Once they start talking they never shut up & then you'll be thinking back to these days, with how blissful it was that they didn't call your name 100x per day😅 {I have a 5 year old as well, this is how I know}.