Really difficult getting and staying pregnant....

So am now 43 and in a fantastic relationship with a wonderful man I have 2 children from a prev marriage he has none we have been trying for a baby for the last year and a half I've had 3 pregnancies all ending in early miscarriages..all very heartbreaking were trying pre seed and I take cq10 and multivitamins anyone else got any tips to conceive and help stay pregnant? Clock is ticking and I'm worried I'm developing poas dependency!