Having spent plenty of time with a chiropracter over the last 12 months I would suggest you work on you core stability and try adjusting you saddle position, try moving it forwards to start with and see where that gets you, it helped me quite a lot.
Planks are probably the best and easiest exercise to strengthen you core at home.
Start with a frontal plank holding you hips inline with your shoulders and ankles and rest on your elbows. Do this for 30 seconds.
do the same but on your side, resting on one elbow, again 30 seconds. Do the other side for another 30 seconds.
Do a reverse (upside down) plank for 30 secs. On your back, take your weight on your shoulders, knees up and feet flat on the floor. Lift your hips high and squuze your ass in.
Do this routine through 2-3 times. As it gets easier you can increase the time of each plank say, up to 45 seconds. When you get really good you can use an inflatable gym ball which will naturally create inbalances that your core muscles have to work harder to counteract and keep you stable.
Unfortunately its something you need to keep on top off, otherwise you just end up back where you started.
Hope this helps.