Hiya, i worked in a dental setting for years (not a dentist)

No, bloods tend not to be diagnostic in a lot of cases. My wife had quite extensive bc in her left breast, and her bloods were always fine. Not what you're wanting to hear, but it is the reality.

In many cases, you need some sort of scan to confirm the presence of a lump, whether that be an US, CT, MRI etc, and if one is found, and warrants further investigation, a biopsy may follow along with other tests (varies depending on where and what type of cancer is suspected). For many cancers, not all, a biopsy is what confirms whether it's cancer or not.

We understand your fear, and it's easy for others to sit here and tell you to push for further tests, but when you're the person being tested, sometimes our mind takes over. But you need to push for other tests because dealing in reality again, fear doesn't change whatever is causing those swellings. Sooner something is seen to whether it be infection or cancer, the easier treatment is in every case. Whilst my wife went to the gp the next day after finding her lump, the cancer was advanced compare to others she met. She needed a lot of treatment compared to those who had their cancer discovered sooner.

Dealing in reality again, almost all lumps tend not to be cancer. You could simply have an infection going on somewhere that can't be picked up via an xray. Xrays tend not to be that great at diagnosing anything other than decay in a tooth or picking up an infection once that infection has begun to cause bone loss (that's what those dark areas are under the infected tooth. The infection eats away at the bone). Go back to your gp, or even ask your dentist for a referral to your local dental hospital. The dental hospital have access to better scans such as cone CTs that pick up issues a lot better than any xray would. Xrays of the teeth are very, very limited. Failing that, the next sensible step would be a referral to the ENT department.