Welcome to Oklahoma diving. . . Ice diving to hot water diving in the late summer. Only a very small number of divers dive year round, I did at one time, but now mostly dive in the summer only, 5 months a year. If you have a 3 mil suit, it will do well those 5 months, May, June, July, Aug, Sept, and usually early October. In May and October I'll usually add a "Beanie" thin head cover with a strap under the chin.
A second wetsuit, can be a 5 mil farmer john. A bib style long leg "bottom" and a waist length, long sleeve top, with 2 layers of material over the core of the body, will extend your diving year to all of October, into November and early December, also April and early May. Depending on surface temps and wind chill index those conditions may stop comfortable diving.
January, February, March are left for the hard core divers, wearing 7mm farmer john suits or dry suits. There are a few dry suit divers who can outlast all the rest of us. . . but your dive buddy must also be wearing a dry suit or you're left alone.
3 mil suits are more comfortable because they are thin. . . A 5 mil suit starts to get harder to move in because of the thickness of the material, and when you increase to a 7 mil suit It is uncomfortable trying to move. All that changes if you order a custom suit that fits you perfectly. A custom suit is a huge improvement in any of the thicker materials. On a dive with my first custom suit, I was with a partner who got cold at the same rate I did, the week before. . . While still warm and wanting to keep diving, my partner, who was shaking ended the dive because he was too cold, we had been down twice the length of time as the week before, and I was still warm. You and your partner must have similar equipment.
Hoods are uncomfortable if they fit you perfectly. . . and torture if they are not perfect. Too tight, with thick material, can feel like it is breaking your jaw, or squeezing your head. A hood can come with a vest, or a skirt to go under your jacket, or a short neck length skirt, depending on the temperature you're trying to endure.
If you dive in colder water, carry a thermos of bath temp water, to pour into your suit at the end of the dive and you'll recover body heat faster. Also, cold water can leave you feeling exhausted, bring something to maintain your blood sugar level.