Positioning the mouth to produce the /m/ sound after the /s/ sound like in the word smoked is actually quite a difficult feet. More difficult than moving from /s/ to /i/ (ee) liek in Sierra Turkey. Perhaps there is something to be said about the level of difficulty of the word before the stuttering word. Most people who stutter have conflicts with specific sounds and words. Can you give some more examples of what words / sound combos? Once you target and isolate those sounds, maybe try saying those words a little bit slower. Over time you will be used to it and it might be worth trying these words slower in the privacy of your own home before going into public so you don't feel 2x embarrassed once you're speaking slower than everyone else. I know speech therapy might be expensive, but it's usually free through a university. I'm a speech-language pathology graduate student. PM me with your location and I would be glad to help you find a graduate program in the area with a clinic that could help you out.