Baby Carrier or No Baby Carrier?

I need help in selecting a good baby carrier for my now four month old baby.

I love carrying my little boy whenever we're out. Thanks to our baby carrier, holding him was very convenient. I was able to hold my little girls hand or bottle feed him when we're out and the head support in his carrier was great for the past two months. Last month, I took it out and he was able to face the front. My little boy is growing so fast, he will be four month old next week, and last Monday was the last day I carried him while doing our indoor walks. I wasn't able to sleep for three days due to shoulder and neck pain, our last checkup showed him weighing 15.3 lbs. I guess it's really his weight that's giving too much pressure, to ease the pain I started taking tylenol and I also looked for chiropractic technologist program and used TENS unit. However, I really need help in deciding: Should I still use a baby carrier? Any recommendation of the kind of baby carrier? Any brand in particular? If I can't find any baby carrier that won't give me shoulder and neck pain, that means his daddy will be the one to hold him everytime we're out.