From my childhood I have offered flower, milk etc to Shiva. But, I have been offering my own creation to Shiva for the last several years. This is very painful is there a known technique to stop such offering?
"I have been offering my own creation to Shiva for the last several years."
You are not offering your own creation. The whole creation which we see and perceive is just apparent modification of Brahman and is characterized by name and form (Nãma Rupa). I discuss in my answer here that everything is Brahman.
Regarding the offerings also Bhagvad Gita states:
ब्रह्मार्पणं ब्रह्म हविर्ब्रह्माग्नौ ब्रह्मणा हुतम् |
ब्रह्मैव तेन गन्तव्यं ब्रह्मकर्मसमाधिना || 24||
BG 4.24: For those who are completely absorbed in God-consciousness, the oblation is Brahman, the ladle with which it is offered is Brahman, the act of offering is Brahman, and the sacrificial fire is also Brahman. Such persons, who view everything as God, easily attain him.
So, you are not giving your own creation to Shiva. You are just offering Brahman to Brahman and that act of offering is also Brahman.