Lumpy two-color knitting

Hi! I’m new on the forum and I need some help. I’m knitting heart sweaters for my granddaughters and I’m having trouble with the hearts. The small one I just knitted on the back looks lumpy. Does it sound like I’m pulling the yarn too tight or too loose? As the heart gets bigger I’m carrying the mc in the back every three stiches. Am I doing something wrong?
Thanks,
NancyPhx

Are you carrying the yarn around the entire sweater…as in fair isle? Or are you doing intarsia?

With fair isle you carry the yarn on the entire project. Usually fair isle (or stranded) knitting is done when the color is carried throughout the area like across in the yoke of a sweater. With intarsia you don’t carry it at all. You twist the yarns at the borders so there is no gap. Intarsia is done for larger blocks of color where you don’t want the contrasting color carried across the main color.

So which are you doing?

For small areas of color where you’re carrying the yarn across the back and catching the yarn every 3-4 sts, the problem is usually that the yarn is being pulled too tightly. If you stretch out the sts on the right needle before you catch the yarn or change to another color, it helps to prevent a tight loop across the back.