No, I don't think that your headaches are migraines, but that's not to say that they aren't severe, or don't deserve followup treatment so that you feel better. Regardless of the severity, migraines typically involve light/sound sensitivity, and are "throbbing" in nature, neither of which are focal points in your description of your headaches. You also either don't list or specifically refute common problems associated with brain tumor headaches (e.g. vomiting, balance problems, etc.)
In fact, it sems that you have already identified the neck tension (and probably muscle spasms) that are triggering your headaches. Have you seen either a physical therapist or a chiropracter? Either one could help with exercises, ultrasound therapy, and use of heat/cold to relieve some of your neck pain. If you are spending long hours at a computer, or in another fairly static position, (especially at work where you are probably already feeling stressed) it may be worth checking out whether there is an ergonomic issue involved. Do talk to your doctor as well since you may benefit from muscle relaxants, and you may need referrals to the other providers, and possibly a MRI of your neck if the conservative measures don't work after a few weeks.