I have been practicing Meditation sice last 25+ years, While i feel that I have benefitted -healthwise, perfect BP and pulse rate generally, but I do not feel that I have progressed much.
I have changed the process of meditation few times:
I get involuntary exhalations during meditation, quite forceful when I go a bit deep with increased focus. I have no Guru but Youtube. When it happens a few times I finish it with a prayer. I have started sitting on a chair instead of floor. Please help.
I think you are ready for your next step with meditation! You have made some progress with your techniques, but meditation must be dynamic, always taking you deeper. Your note indicates you long for this.
I encourage you to take a look at our Ananda Course in Meditation, a 10-week online course which includes training in the Hong-Sau technique of meditation, and Energization which was a technique introduced by Yogananda. The course also has group meditation, reading, and videos teaching the principles of meditation in-depth, as well as a weekly opportunity for online group guided meditations to work with these practices. You can learn about this course here: Ananda Course in Meditation Online.
This course is designed for students who come from various traditions who seek to deepen their practice. Students participate from all over the world. Many have been meditating for quite a while and discover how much their practice is renewed and deepened by this course. If you are inspired by what you learn, further teaching in meditation and the spiritual path are available as next steps after this course.
Please check it out. New sessions start approximately monthly.