What am I doing wrong? It might be implantation bleeding but is heavy and not spotting.

When is your period actually due? How long have you been trying to become pregnant?

Most couples will become pregnant within a year of trying, but for some it can take a bit longer... even when everything is fine. This is why you only have about a 20-25% chance of becoming pregnant in any given cycle.

If you were to notice implantation spotting/bleeding, and most women don't, it most often is short term and just spotting. You can, however, have some heavier bleeding in early pregnancy for a number of possible reasons.

You may be doing nothing wrong at all and it will just take a bit more time. How have you determined when you are most likely ovulating?

Three months is how long I have been trying. My period was supposed to come two days afterwards and I use the ovulation calculator on justmommies.com and ovulation test to predict ovulation and have done it when ovulating both times.

Those ovulation tests are strictly predictors. It's impossible to know exactly when you ovulate.

As Doula has said, it can take the average healthy couple up to a year of actively trying before actually conceiving.

I know it's hard, but don't get frustrated. It just takes time.