My once extremely loyal dog isnt loyal anymore 😖

I'm 15 weeks pregnant and my 4 year old dog has taken to running away from home.. we have a puppy also who is only 6 months but he doesn't leave.. my dog never used to leave my side but now hes constantly running off and stressing me out.. he got picked up by the ranger today and we had to pay a $220 AUD fine even though he called me and he is fully vaccinated, microchipped, registered and has a tag 😖😖 he stresses me so much he used to be my baby now he couldn't care less about me 😪