Ive been going to the gym 4-5 times a week for the past 3 weeks, after my 4th week do u think its time to change up the routine a little? heres what im doing now

Mon: 3-Chest 2-Tricep
Tues: 5-Shoulder
Wednesday: 4-Back 2-Bi
Thursday: 5-Leg
Friday: 40min Cardio 3-Ab

I do cardio mon-thurs for about 15 minutes before my workout... This may seem like a little awkward break down but its been working for me... Gained 6lbs in 3 weeks and my waist has gotten smaller (wear my belt 1-2 nothces tighter now)

Should I mix it up a little.. maybe something like

Mon: 3-Bi, 3-Tri
Tues: 4/5 Chest
Wednesday: 5-Legs, 3-abs
Thursday: 4-Back
Friday: 5 Leg, 3ab
*of course i wouldnt cut out my cardio but maybe do my 12 minutes on weekdays then saturday ill do the 40 minutes

It would probably be a good a idea to rest for a week, then start a new routine. Why not try something that will work each each muscle group twice or thrice a week? Focus on big compound lifts (Squat, deadlift, bench, pullups, row, and shoulder press). If you're planning on changing every 4 weeks or so, that gives you the chance to try something for a few weeks, and if it doesn't result in gains, you can change it.
Also, blasting your triceps on Monday will hurt your chest workout on Tuesday because your arms might be too weak to lift as much weight as you should to really work the pecs.