SSP is paid at a standard rate so do you mean SSP or do you mean company sick pay? If it IS SSP and you think it is wrong, you should contact HMRC (they used to be the Inland Revenue) as they run the system and they�ll be in the local �phone book. They may give you another number as they have various centres covering different parts of the country.
You should �phone ACAS for advice too, they are open Monday - Friday 08:00 - 18:00 - 08457 47 47 47.
With reference to SSP and pregnancy, there is a link. If you receive SSP for a pregnancy related illness at the start of or in the 4 weeks before the wee one is due, SSP will stop and any entitlement to Statutory Maternity Pay (SMP) or Maternity Allowance (MA) will start automatically.
Also what was said about not getting paid for the first three days each time is incorrect. Those three days are called waiting days and if the spells of sickness were separated by 56 days or less, the spells are counted as being linked and the waiting days would not be applied again.