I always feel like i have to crack my neck even though it is not sore or tight. is this a bad habit?

Cracking neck: Most of the time cracking a joint simply pops a nitrogen bubble out of the joint. There is no harm as nitrogen diffuses back into the joint quickly. Consider this scenario as merely a repositioning of a joint. If the crack, however, is associated with pain, this indicates a more serious problem and should be evaluated by a spine specialist asap.

No it is muscular: This is ok and you are doing your own spinal manipulation like cracking your knuckles. You are most likely "cracking" your facet joints (the small joints of the spine-2 at each level) which stretches their joint coverings or capsules which causes a reflex relaxation of the surrounding muscles. There is no harm in you doing this.