Lately I feel that I don't have any sexual desire especially after I was diagnosed 6 months ago with having fibromyalgia. Iam taking lyrica (pregabalin) &effexor75?

Address now. This needs to be addressed as lack of sex drive can lead to frustration, depression, and loss of intimacy between couples. The lack may be a side-effect of one of the medications. If the lack is due to depression, that also would need to be addressed. The good news is that sex and exercise can be helpful is treating fibromyalgia.
Side effect. You may be experiencing a side effect of effexor (venlafaxine). Since this is a new issue, it is not likely related to your fibromyalgia.
Side effects. Both those medications can decrease your libido. You are going to have try ways to increase your libido. Plan dates, exercise, try therapeutic yoga. Andrew weil's new book, " spontaneous happiness" may be a good start.